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The lost art of joy – Learning

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Solomon wrote: “Of the making of many books there is no end, and much study is a weariness unto the flesh”.

I loved that verse when I was at school. It was utilised more than once when my teachers wanted to give us more homework – “But, sir, the Bible says that too much homework is bad for you.” Not that my teachers cared, they just gave me more homework anyway.

Much study may be a weariness unto the flesh, but some study is actually very beneficial. Learning helps to promote joy, and joy helps to promote learning.

It’s been shown that learning is much easier when there’s joy involved. Co-founder of the NeuroLeadership Institute, Dr David Rock said,

“Engagement is a state of being willing to do difficult things, to take risks, to think deeply about issues and develop new solutions … Interest, happiness, joy, and desire are approach emotions. This state is one of increased dopamine levels, important for interest and learning.”

and

“There is a large and growing body of research which indicates that people experiencing positive emotions perceive more options when trying to solve problems, solve more non-linear problems that require insight, [and they] collaborate better and generally perform better overall.”

This makes sense. According to the classical psychology principle of the Yerkes-Dodson law, optimal task performance occurs at an intermediate level of arousal, with relatively poorer performance at both lower and higher arousal levels. Too much stress (anxiety) or not enough stress (boredom) results in reduced performance. When someone is happy and engaged, their learning is at its optimum level.

But while it’s true that happiness and engagement create the optimal conditions for learning, it’s also true that learning created a sense of joy.

Learning new things is stimulating. Exposure to new information makes the brain work harder. We are very predictive creatures, and our brain has adapted to be predictive because it’s the most efficient way of processing the vast amount of information that we come across each day. After a while of being exposed to the same stimuli, our brains get a bit lazy. There’s no need to grow new branches and our brains become a bit stagnant. There’s no stimulation, so there’s no dopamine rush. We just get into our rut. But being exposed to new experiences, to new stimuli, is invigorating. Our brain can not longer rely on the same old predictive pathways, and new parts of the brain need to be engaged to process all of the different things we’re being exposed to. The dopamine cloud that comes from all of the novel stimuli is quite euphoric.

Learning something new helps our brain to stay supple. The brain is like a muscle – the only way to keep it flexible and strong is to exercise it. By constantly providing stimulation, our brain can better cope when unexpected events occur, because we’re already used to novel challenges. It helps us stay resilient by improving our psychological flexibility.

Learning something new can also give us a sense of accomplishment which is always good for our self-esteem and self-confidence.

There are many ways to learn new things – read new books, or if you’re not the reading type, find some interesting, factual documentaries. A great way of stimulating your brain is to learn a second language, which also gives you a great excuse to do the other thing that helps to grow your brain and your joy, which is to travel to a different country. Trying to speak a new language in a foreign country will really give your brain a workout, which may seem very daunting at first, but will help you grow immensely. You can also learn a new skill like craft, or a musical instrument. Your learning doesn’t just have to be about yourself – learn to juggle or make balloon animals, and use those skills to entertain people, or put a smile on a child’s face. That way the joy is shared through learning and giving.

Just remember your values when deciding what you would like to learn so that your learning is in step with your authentic self and enriches your life. And make sure you keep your work and life in balance as you carve out time to learn something new, all that study doesn’t become a weariness unto the flesh.

Don’t stress about stress – Part 4: Stress breaking bad

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This is the last blog post in my brief series on stress. Today, we’re going to look at what happens when we do hit stress overload, and a few simple methods that may be able to help you through a tough situation.

One of my favourite shows of all time was Breaking Bad. Breaking Bad told the story of Walter White, a high school chemistry teacher and average family man, who is diagnosed with terminal lung cancer. To support his wife and disabled son after he’s gone, he uses his knowledge of chemistry to launch himself into an underworld career manufacturing crystal meth.

Allostatic overload is the term modern scientists use for stress breaking bad. Stress moves from an agent of growth and change to an agent of disease and death.

In the last few blogs, we discussed that stress is actually more of a positive than a negative. It’s not that stress can’t be bad, because we know from the stress-productivity curve and from the Yerkes-Dodson Law that too much stress overwhelms our capacity to cope with it. The model used to describe the balance of stress on our body is the theory of Allostasis.

Allostasis

All living things maintain a complex dynamic equilibrium – a balancing act of the many different physiological systems that all rely on the other systems working at an optimal range. Imagine trying to stack ten spinning tops on top of each other while trying to keep them spinning. The body does the chemical equivalent of this very difficult combination of balance and dexterity every day. It’s called homeostasis. This balancing act is constantly challenged by internal or external events, termed stressors. Both the amount of stress and amount of time that the stressor is applied is important. When any stressor exceeds a certain threshold (“too strong, or too long”), the adaptive homeostatic systems of the living thing activate responses that compensate.

The theory of allostasis is related to these homeostatic mechanisms, although not just in terms of stress, but broadly to the concept of any change of the optimal range of these homeostatic balancing processes, in response to a change in the environment or life cycle of an organism [1].

McEwen and Wingfield give an example of some bird species, which change their stress response to facilitate their breeding capacity during mating season. They note that the benefit of the increased chance of breeding is important to the bird, but also comes at a cost of increased susceptibility to some diseases because of the weakening of the stress response at the time [1].

When it comes to stress, we adapt in a similar way. A lack of stress, or an excess of a stressor in some way (either too long or too strong) results in adaptation, which is beneficial, but can come at a cost. This is demonstrated by that broadly applicable U-curve, the stress productivity curve.

Chrousos wrote, “The interaction between homeostasis disturbing stressors and stressor activated adaptive responses of the organism can have three potential outcomes. First, the match may be perfect and the organism returns to its basal homeostasis or eustasis; second, the adaptive response may be inappropriate (for example, inadequate, excessive and/or prolonged) and the organism falls into cacostasis; and, third, the match may be perfect and the organism gains from the experience and a new, improved homeostatic capacity is attained, for which I propose the term ‘hyperstasis’.” [2] And as noted by McEwen, “Every system of the body responds to acute challenge with allostasis leading to adaptation.” [3]

More often than not, we adapt to the stressor, either the same as before, or possibly better. It’s only if the response to the stressor is inadequate, excessive and/or prolonged that stress ends up causing us trouble. This is what people normally think of when they think of stress – called allostatic overload – simply stress breaking bad.

Keeping stress in check

To ensure that we keep our stress levels at the optimum to ensure maximum productivity and growth, here are a few simple techniques. Remember, everyone handles stress differently, and so which of these techniques works best for you will be something you’ll have to learn by trying them.

Breathing

The simplest tool is breathing. Sounds a little silly really, since you obviously breathe all of the time! But we usually take shallow breaths, so our lungs are not being used to their full capacity. When we focus on our breathing and deliberately take slow, deep breaths we increase the amount of air going in, and therefore allow more oxygen to enter the blood stream. This better fuels our cells and helps them do their job more efficiently. However, it also sets in motion a physiological mechanism that slows our heart rate.

Our heart pumps blood from our body, through the lungs to get oxygenated. As we take a deep breath, more blood is sucked up into our chest cavity from our veins, because breathing in causes a temporary vacuum in our chest cavity. The extra blood then fills our heart more efficiently. A more efficient heart beat reduces the need for the body to stimulate the heart to pump harder. This promotes more of the parasympathetic “rest-and-digest” nervous system activity, and less of the sympathetic “fight-or-flight” nervous system, via the vagal brake mechanism.

So, to slow your breathing down simply sit in a comfortable position. Take slow, deep breaths, right to the bottom of your lungs and expanding your chest forward through the central “heart” area. Count to five as you breathe in (five seconds, not one to five as quickly as possible) and then count to five as you breathe out. Keep doing this, slowly, deeply and rhythmically, in and out. Pretty simple! This will help to improve the efficiency of your heart and lungs, and reduce your stress levels.

Remember, B.R.E.A.T.H.E. = Breathe Rhythmically Evenly And Through the Heart Everyday.

Meditation

Meditation takes the techniques of breathing one step further, in that meditation involves deliberately switching your brain’s focus to something simple, and in the present. Focussing on nothing – just breathing and turning off your thinking for while – does take some practice. Concentrating on something in the present (not thinking about the past or the future), tends to be easier and requires less practice, although ignoring all the other thoughts that routinely clamour for your attention might be hard when you first try it.

Focusing on the present moment is part of the practice of Mindfulness. Mindfulness meditation has been studied quite extensively over the last few decades, and has been shown to have benefits over a large number of psychological symptoms and disease states [4].

Sometimes it is easier to focus on something visual, that you can see easily in your field of view, or listen to something constant, like the ocean, or a metronome. The easiest thing to do is to again, focus on your breathing. Concentrate on the sound, rhythm and feeling of your breathing, but don’t engage your thoughts, or allow others to creep in. Meditation quietens the mind, which is excellent for reducing stress, and can help to revitalise and refresh your mind.

Guided Imagery

Guided imagery is a step along from meditation. Instead of focussing on something tangible, guided imagery lets you imagine that you are somewhere pleasant, relaxing, or rejuvenating. Some people describe it as a vivid daydream.

Get comfortable, close your eyes and start to breathe slowly and deeply. Once you begin to relax, imagine your favourite scene. It could be at the beach, or in a log cabin in the snow-capped mountains, or swimming in the cool waters in a tropical rain-forest. Whatever you choose, try to imagine the scene in as much detail as possible, and involve all five of your senses if you can, like, for example, the cool water of the waterfall on your bare skin, the sounds of the birds in the trees, the smell of the moss-covered rocks, the canopy of tall trees and vines split by the waterfall and stream allowing the sunlight to spill in to the forest floor. Enjoy the details and the relaxation that this brings. To “come back”, some recommend counting back from ten or twenty, and to tell yourself that when you reach one, you will feel calm and refreshed.

Guided imagery allows you to actively replace the harassing thoughts of your daily routine with pleasant soothing thoughts. There is some early scientific literature suggesting effectiveness, although more research is required [5, 6]. Again, with practice, this can be done anywhere, and can be done quickly if you need a short break to unwind.

Visualisations

Visualisations build on the techniques of guided imagery, but instead of the rain-forest or tropical paradise, you imagine yourself achieving goals, which again could be anything from improving your health, closing that deal, or hitting that perfect drive from the first tee. Again, try and imagine the scene in as much detail as you can, and involve all of your senses.

PMR

Progressive Muscle Relaxation, or PMR for short, is similar to meditation, except that you contract, hold, and then relax your muscle groups in turn. You concentrate on the feel of the tightening and relaxing of the muscles instead of, or as well as, your breathing. Like meditation, it can be done anywhere and involves very little training.

The contraction of the muscle groups, beginning in your feet – working your way up the calves and thighs, tummy, chest, arms and neck, sequentially pumps all of the blood back towards your heart, giving you a boost of blood flow to your lungs. The deep breathing oxygenates this extra blood and hence, gives your brain a burst of oxygen.

Using PMR to meditate helps engage the vagal brake, and there is some evidence that it helps to reduce persistent pain [7, 8].

Exercise

Exercise releases stress and enhances your physical health [9, 10]. It is flexible and easily adaptable – it is usually free and can often be done without any equipment. The downside is that it is not possible everywhere (you can’t go jogging in a plane), but as a daily discipline, it will enhance your physical and emotional wellbeing.

The benefits of exercise are firstly physical. It gets your heart pumping, the blood flowing and your lungs working to their full capacity. It builds physical fitness, which is important to enable the heart and lungs to work efficiently at all times. Exercise has effects on mood, improving depression [11] and anxiety [12].

It can also act as a form of meditation – the solitude of a run or swimming a few laps, concentrating only on the splash of your strokes or the pounding of your feet on the ground – is similar to meditation except that you’re moving (whereas meditation proper involves being still and relaxed). But the outcome is the same, and stress is often reduced by a session of physical exercise.

Music

Music is almost as fundamental to human existance as breathing, and it’s almost as diverse as mankind itself. Listening to ones favourite music can enhance feelings of control and can increase pain tolerance and improve short term anxiety (stress) [13]. The common characteristics of ‘therapeutic’ music was music which had less tonal (pitch) variation, less prominent chord changes, bass lines, or strong melodies [14].

But the key element was personal preference overall, as some of the participants in the study chose music like Metallica. So enjoy music. Make it part of your day. Even Country and Western may be considered therapeutic!

Yoga

Yoga is an ancient practice that has several components including physical postures (asanas), controlled breathing (pranayama), deep relaxation, and meditation.

It’s not for everyone, but it has clearly defined and scientifically validated benefits to your physical and psychological well-being. “It is hypothesized that yoga combines the effects of physical postures, which have been independently associated with mood changes and meditation which increases the levels of Brain-derived neurotrophic factor (BDNF). Other effects that have been noted include increased vagal tone, increased gamma-amino butyric acid (GABA) levels, increase in serum prolactin, downregulation of the hypothalamic-pituitary-adrenal axis and decrease in serum cortisol, and promotion of frontal electroencephalogram (EEG) alpha wave activity which improves relaxation.” [15] So, translated: Yoga is good for stress relief!

Most gyms and community centres will have yoga instructors, so go ahead and make some enquiries.

Massage

I love massage! The first time I had a proper massage was in the small city of Launceston in the tiny Australian state of Tasmania. After just 30 minutes of the therapist kneading my muscles with her fingers of iron, I felt pretty good, but when I sat up, I was actually light-headed for a little while. My heart rate and blood pressure had reduced so much that it took me a while before I could stand up properly!

Deep pressure massage has also been shown to help release the vagal brake enhancing the activity of the parasympathetic (rest-and-digest) part of the autonomic nervous system. There is good evidence of this effect in pre-term infants [16]. The evidence for adults isn’t so strong, although that’s probably because of a lack of quality research [17]. The good studies that have been done show a reduction of cortisol, blood pressure and heart rate after massage, with some studies showing small persistent effects [17].

The data might be thin, but there is enough evidence to make it worth trying at least once.

Probiotics

I add probiotics to this list as a reference for the future. There is good evidence of the anxiolytic effect of having a friendly bacteria garden in your intestines that interacts with your gut and your immune system in positive ways. But there is, at this point, very little in the way of good quality human clinical trials. And we still don’t know exactly which strains of probiotics are the most helpful for different conditions [18, 19]. But given that they are unlikely to be harmful, it may be worth trailing a course of probiotics, and see how you feel in 30 days.

The bottom line – stress is not the enemy. Sure, if it isn’t handled right, stress can overwhelm us and make us sick, but most of the time, stress makes us productive and strong, and helps us to grow. So, don’t stress about stress.

References

  1. McEwen, B.S. and Wingfield, J.C., What is in a name? Integrating homeostasis, allostasis and stress. Horm Behav, 2010. 57(2): 105-11 doi: 10.1016/j.yhbeh.2009.09.011
  2. Chrousos, G.P., Stress and disorders of the stress system. Nat Rev Endocrinol, 2009. 5(7): 374-81 doi: 10.1038/nrendo.2009.106
  3. McEwen, B.S., Stressed or stressed out: what is the difference? J Psychiatry Neurosci, 2005. 30(5): 315-8 http://www.ncbi.nlm.nih.gov/pubmed/16151535
  4. Keng, S.L., et al., Effects of mindfulness on psychological health: a review of empirical studies. Clin Psychol Rev, 2011. 31(6): 1041-56 doi: 10.1016/j.cpr.2011.04.006
  5. Jallo, N., et al., The biobehavioral effects of relaxation guided imagery on maternal stress. Adv Mind Body Med, 2009. 24(4): 12-22 http://www.ncbi.nlm.nih.gov/pubmed/20671330
  6. Trakhtenberg, E.C., The effects of guided imagery on the immune system: a critical review. Int J Neurosci, 2008. 118(6): 839-55 doi: 10.1080/00207450701792705
  7. Baird, C.L. and Sands, L., A pilot study of the effectiveness of guided imagery with progressive muscle relaxation to reduce chronic pain and mobility difficulties of osteoarthritis. Pain Manag Nurs, 2004. 5(3): 97-104 doi: 10.1016/j.pmn.2004.01.003
  8. Morone, N.E. and Greco, C.M., Mind-body interventions for chronic pain in older adults: a structured review. Pain Med, 2007. 8(4): 359-75 doi: 10.1111/j.1526-4637.2007.00312.x
  9. Fletcher, G.F., et al., Statement on exercise: benefits and recommendations for physical activity programs for all Americans. A statement for health professionals by the Committee on Exercise and Cardiac Rehabilitation of the Council on Clinical Cardiology, American Heart Association. Circulation, 1996. 94(4): 857-62 http://www.ncbi.nlm.nih.gov/pubmed/8772712
  10. Warburton, D.E., et al., Health benefits of physical activity: the evidence. CMAJ, 2006. 174(6): 801-9 doi: 10.1503/cmaj.051351
  11. Rimer, J., et al., Exercise for depression. Cochrane Database Syst Rev, 2012. 7: CD004366 doi: 10.1002/14651858.CD004366.pub5
  12. DeBoer, L.B., et al., Exploring exercise as an avenue for the treatment of anxiety disorders. Expert Rev Neurother, 2012. 12(8): 1011-22 doi: 10.1586/ern.12.73
  13. MacDonald, R.A., Music, health, and well-being: a review. Int J Qual Stud Health Well-being, 2013. 8: 20635 doi: 10.3402/qhw.v8i0.20635
  14. Knox, D., et al., Acoustic analysis and mood classification of pain-relieving music. J Acoust Soc Am, 2011. 130(3): 1673-82 doi: 10.1121/1.3621029
  15. Balasubramaniam, M., et al., Yoga on our minds: a systematic review of yoga for neuropsychiatric disorders. Front Psychiatry, 2012. 3: 117 doi: 10.3389/fpsyt.2012.00117
  16. Field, T., et al., Preterm infant massage therapy research: a review. Infant Behav Dev, 2010. 33(2): 115-24 doi: 10.1016/j.infbeh.2009.12.004
  17. Moraska, A., et al., Physiological adjustments to stress measures following massage therapy: a review of the literature. Evid Based Complement Alternat Med, 2010. 7(4): 409-18 doi: 10.1093/ecam/nen029
  18. Bested, A.C., et al., Intestinal microbiota, probiotics and mental health: from Metchnikoff to modern advances: Part II – contemporary contextual research. Gut Pathog, 2013. 5(1): 3 doi: 10.1186/1757-4749-5-3
  19. Bested, A.C., et al., Intestinal microbiota, probiotics and mental health: from Metchnikoff to modern advances: part III – convergence toward clinical trials. Gut Pathog, 2013. 5(1): 4 doi: 10.1186/1757-4749-5-4

Bad choices cause brain damage?

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“To err is human; to forgive, divine.”  Alexander Pope.

I’m not perfect.  At least, not the last time I checked.  And we’re all the same, aren’t we.  We all know through experience that we all stuff things up on a fairly regular basis.  We make bad choices.  We’re human!

Dr Caroline Leaf, Communication Pathologist and self-titled Cognitive Neuroscientist, believes that these bad choices literally cause brain damage.  Her fundamental assumption is that our thoughts control our brain [1: p33].  These thoughts can be healthy or they can be toxic.  Toxic thoughts “are thoughts that trigger negative and anxious emotions, which produce biochemicals that cause the body stress.” [2: p19]

Dr Leaf’s assumption is that thoughts and bad choices cause our brain cells to shrivel or die. “Once your body is truly in stress mode and the cortisol is flowing, dendrites start shrinking and even ‘falling off’” [2: p32].  She also says that, “We have two choices, we can let our thoughts become toxic and poisonous or we can detox our negative thoughts which will improve our emotional wholeness and even recover our physical health.” [2: p21]

It sounds a little extreme.  We all make bad choices, and we all experience stress.  When we’re stressed, do our memories really go missing, or the dendrites of nerve cells shake and fall like tree branches in a storm?  If we make a bad choice, do we really get brain damage?  Lets see what the scientific literature has to say.

Imagine walking along a path in a forest and you see a snake, only inches in front of you on the path.  What do you do? When faced with a high level of acute stress, the brain switches into a binary mode – fight/flight or freeze. Self-preservation has to kick in.  The only decision you have to make then and there is whether to run, to try and kill the snake before it kills you, or stop dead still and hope that the snake ignores you and slithers away.

At that point, most memory is redundant, as is a high-level analysis of snake species, or any other cognitive pursuit.  The brain doesn’t need them at that precise moment.  If they did engage, they would just get in the way.  Switching the thinking parts of your brain off focuses your attention on the immediate danger.  It’s an adaptive survival response.  Meantime, your memories and your theoretical knowledge about snakes don’t disappear.  They are still there, unchanged.  It is false to suggest that the memories “shrink”.

We’ve all experienced “mental block”.  Sometimes when we get into a situation, like an exam or a business meeting, our stress levels are high, and binary mode kicks in again, although this time it can be a hindrance.  This phenomenon of mental block under high stress was first proposed in 1908 and is currently known as the Yerkes-Dodson Law, a fundamental principle of the behavioural sciences [3].  Similar to the stress-productivity curve, Yerkes and Dodson proposed a U-shaped curve to represent the relationship between arousal (which could be either level of consciousness or stress) and behavioural performance.  At low arousal, there is poor performance.  At the mid-point of arousal, there is peak performance, and at high arousal, performance diminishes.

But again, our memories don’t shrink, and our nerve cell branches don’t fall off.  Once we reduce our level of arousal, we move away from the fight/flight/freeze mode, and everything is still there (and we perform better, according to Yerkes-Dodson).

Dr Leaf has a favourite analogy of “neurons as trees”.  And if neurons are trees, then the branches can “fall off”.  But neurons are not trees and dendrites are not tree branches.  The dendrites do not ‘fall off’ the neuron.  The neurons in the brain have mechanisms for ongoing brain plasticity – the ability of the brain to adapt to the challenges and changes in its internal and external environment that are constantly occurring.  If the brain needs to build a new circuit to encode a new piece of information, then it grows new dendrites and creates new synapses.  But the brain is limited by the amount of energy it can consume, and therefore the number of synapses it can maintain.  So the brain trims unnecessary dendrites, a process called “synaptic pruning”.

Synaptic pruning is a normal process. Chechik and Meilijson confirm that, “Human and animal studies show that mammalian brains undergoes massive synaptic pruning during childhood, removing about half of the synapses until puberty.” [4]

Synaptic pruning is not deleterious, but beneficial.  Chechik and Meilijson also note that, “synaptic overgrowth followed by judicial pruning along development improves the performance of an associative memory network with limited synaptic resources.” [4] So synaptic pruning is a normal physiological process, and occurs in all of us for many reasons, predominantly to improve the efficiency of our neural networks.  Perhaps synaptic pruning associated with the stress response is also an adaptive process?

Synaptic pruning also occurs in other physiological states that have nothing to do with stress or thought, such as the effects of oestrogen during the menstrual cycle and at menopause [5, 6].

A link between stress and dendrite loss has been discovered, but it is not consistent.  Some authors like Kopp and Rethelyi suggest that “severe stress for a prolonged period causes damage in hippocampal pyramidal neurons, especially in the CA3 and CA4 region and reductions in the length and arborization of their dendrites.” [7] However, Chen et al writes, “Whereas hippocampus-mediated memory deficits commonly were associated with—and perhaps result from—loss of synapse-bearing dendrites and dendritic spines, this association has not been universal so that the structure–function relationship underlying the effects of stress on hippocampal neurons has not been resolved.” [8]

It’s more accurate to think that chronic stress causes dendritic remodeling in animals [9], in which some nerve cells prune their synapses, which others grow them, and energy is diverted away from new nerve cell formation to the new synapses that are needed to cope with the stress.

A number of scientists have pointed out that patients with depression or anxiety, who normally have high levels of stress, have a smaller hippocampus and larger amygdala, so stress and depression must cause the smaller brain regions [9].  There may be some reduction in the number of synapses within the hippocampus and the frontal lobes of the brain, which may account for the change in size observed by a number of researchers.  But the modern thinking on these changes is that they are associated with depression, not caused by depression [10] (Correlation does not equal causation).

So, stress is associated with depression, but this is because genetic defects in one or multiple genes reduce the ability for the brain cells to produce synaptic branches.  It’s this decrease in the number of synapses that contributes to the typical changes in the brain seen at autopsy of patients who suffered from depression or anxiety [11].  The reduced ability of the nerve cells to grow synapses means that new branches can’t grow fast enough to process the stress signals properly [11, 12].  The poor signal transmission leads to a predisposition towards mood disorders like anxiety and depression [10, 11, 13-15], and less synaptic branches means both a smaller volume of the hippocampus, and an inability to process stress signals leads to a larger, overactive amygdala.

In summary, synaptic pruning is not due to toxic thinking or bad choices, unless every one of us engages in nothing but toxic thinking from early childhood to puberty, and menopause causes bad choices and toxic thoughts.  Stress doesn’t cause dendrites to fall off, but causes a reorganization of the dendrites to adapt to the new signals. The reduced capacity to form new dendrites makes those prone to mood disorders more vulnerable to stress, and depression or anxiety is the end result.

We are all bound to make bad choices and to have stress.  They don’t cause brain damage.  Which if you’re not perfect like me, is good news.

References

1.         Leaf, C.M., Switch On Your Brain : The Key to Peak Happiness, Thinking, and Health. 2013, Baker Books, Grand Rapids, Michigan

2.         Leaf, C., Who Switched Off My Brain? Controlling toxic thoughts and emotions. 2nd ed. 2009, Inprov, Ltd, Southlake, TX, USA:

3.         Cohen, R.A., Yerkes–Dodson Law, in Encyclopedia of Clinical Neuropsychology, Kreutzer, J.S., et al., Editors. 2011, Springer Science+Business Media LLC: New York ; London. p. 2737-8.

4.         Chechik, G., et al., Neuronal regulation: A mechanism for synaptic pruning during brain maturation. Neural Comput, 1999. 11(8): 2061-80  http://www.ncbi.nlm.nih.gov/pubmed/10578044

5.         Chen, J.R., et al., Gonadal hormones modulate the dendritic spine densities of primary cortical pyramidal neurons in adult female rat. Cereb Cortex, 2009. 19(11): 2719-27 doi: 10.1093/cercor/bhp048

6.         Dumitriu, D., et al., Estrogen and the aging brain: an elixir for the weary cortical network. Ann N Y Acad Sci, 2010. 1204: 104-12 doi: 10.1111/j.1749-6632.2010.05529.x

7.         Kopp, M.S. and Rethelyi, J., Where psychology meets physiology: chronic stress and premature mortality–the Central-Eastern European health paradox. Brain Res Bull, 2004. 62(5): 351-67 doi: 10.1016/j.brainresbull.2003.12.001

8.         Chen, Y., et al., Correlated memory defects and hippocampal dendritic spine loss after acute stress involve corticotropin-releasing hormone signaling. Proc Natl Acad Sci U S A, 2010. 107(29): 13123-8 doi: 10.1073/pnas.1003825107

9.         Karatsoreos, I.N. and McEwen, B.S., Psychobiological allostasis: resistance, resilience and vulnerability. Trends Cogn Sci, 2011. 15(12): 576-84 doi: 10.1016/j.tics.2011.10.005

10.       Palazidou, E., The neurobiology of depression. Br Med Bull, 2012. 101: 127-45 doi: 10.1093/bmb/lds004

11.       Karatsoreos, I.N. and McEwen, B.S., Resilience and vulnerability: a neurobiological perspective. F1000Prime Rep, 2013. 5: 13 doi: 10.12703/P5-13

12.       Russo, S.J., et al., Neurobiology of resilience. Nature neuroscience, 2012. 15(11): 1475-84

13.       Felten, A., et al., Genetically determined dopamine availability predicts disposition for depression. Brain Behav, 2011. 1(2): 109-18 doi: 10.1002/brb3.20

14.       Bradley, R.G., et al., Influence of child abuse on adult depression: moderation by the corticotropin-releasing hormone receptor gene. Arch Gen Psychiatry, 2008. 65(2): 190-200 doi: 10.1001/archgenpsychiatry.2007.26

15.       Hauger, R.L., et al., Role of CRF receptor signaling in stress vulnerability, anxiety, and depression. Ann N Y Acad Sci, 2009. 1179: 120-43 doi: 10.1111/j.1749-6632.2009.05011.x