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Did you know that how you think affects your health?
That is one of the larger findings from the field of positive psychology. For example, those with a more optimistic perspective live longer, can recover from illness faster, and are more likely to engage in positive health behaviors (exercising, not smoking, etc…). This research article is a review of 137 studies which explore the relationship between positive thought and positive health.
Positive Psychology and Health
This article focuses on 4 specific elements:
- The research in positivity and health that predates the positive psychology movement.
- The possible mechanisms through which positive thought impacts health.
- Four misconceptions about positive psychology.
- Prescriptions against the serious pitfalls that popular views of positive thinking represent to progress and science
Three Positivity Strategies That Impact Health
The authors mention three strategies in particular that have been explored before the rising popularity of positive psychology: Sense of Coherence, Optimism, and Benefit-finding and Growth.
When illness or misfortune strike, those who are able to derive meaning from the crisis, and maintain or improve their sense of coherence, recover faster.
To quote directly from the article – “The robust literature on optimism in relation to health psychology has been recently reviewed [26, 27]. Dispositional optimists tend to engage more frequently in approach-oriented forms of coping, to be flexible in their use of adaptive coping strategies in regard to controllability of stressors , and to have greater perceived capability to manage potentially traumatic events . Optimism has been associated with better coping with a variety of health problems (e.g., breast cancer [30, 31] and human immunodeficiency virus [HIV] infection ). Optimism is also associated with positive health behaviors [32, 33], better recovery from certain medical procedures , positive changes in immune system functioning , and improved survival rates [33, 35].”
Benefit-finding is essentially post-traumatic growth. Martin Seligman recently introduced into the US Military a program for increasing resiliency. The point of increasing resiliency is to make the stress of war trigger post-traumatic growth, rather than PTSD. The benefit of post-traumatic growth is an increase in sense of meaning, personal growth, and the avoidance of the negative symptoms associated with poor handling of stressful situations.
How does positive thought impact health?
First, the authors make clear that the studies they reference track both short-term and long-term health outcomes, to ensure that the changes aren't just tiny, short bumps.
The mechanisms of action can be split into two categories: social/behavioral and neuroendocrine/immune.
There are multiple social/behavioral channels:
- Those that are optimistic are more likely to engage in preventative health behavior, such as exercising more and having a better diet. One explanation for this change is that those that are positive are more likely to believe in internal control, while the negative are more likely believe in external control (to be fatalists) – believing that their fate is out of their control (and are therefore less likely to attempt to change their behavior for the positive). [32,33, 51]
- Those with positive affect are more likely to have social support. Social support can generate resources and knowledge to fight illness, as well as having its own positive effects on health. [46, 53-55]
- Those that are optimistic are more likely to pay attention to health risks, and therefore are less likely to smoke or engage in unsafe sex. [48-50, 52]
Again, there are multiple neuroendocrine/immune channels:
- It is suggested that negative affect induces dysregulation of the systems that would fight illness and cancer, and that positive affect improves their performance. [59, 60] One such system is the immune system – whose activity can sometimes leads to positive changes (e.g. fighting an infection or cancer), or to negative changes (e.g. creating unneeded inflammation).
- One such system is the hypothalamic-pituitary axix (HPA). Dysregulation of the axis is implicated in a host of illnesses: anxiety disorder, bipolar disorder, insomnia, post-traumatic stress disorder, borderline personality disorder, ADHD, major depressive disorder, burnout, chronic fatigue syndrome, fibromyalgia, and irritable bowel syndrome. In addition, dysregulation of the axis reduces the bodies ability to adapt to and/or fight a stressor. 
One great research finding is that these benefits are observed both in people who are naturally happy, and those who receive optimism interventions. [62,63]
Positive Psychology Misconceptions
Positive Thoughts and Feelings Undermine Decision-making, Especially for Negative Information
This is an area I will investigate further at a later time, as the authors don't make a clear case in dispelling the ‘misconception'. They first point to a research review that asserts that positive mood decreases the quality of attention to information and increases avoidance of negative information (“through mood-congruent processing, motivations to maintain a positive mood, information that the environment is safe and one can relax vigilance to negative information or through distraction caused by the large and diverse set of associations primed by positive mood”). 
According to the authors, there are three decades of evidence which refute this viewpoint, that in fact positive affect compared to neutral affect promotes “more thorough and efficient decision-making, greater flexibility in judgment, and better management of risk.” [75, 76] In addition, research has shown that positive affect “promotes adaptive responses to new and potentially useful negative information.” [86-88]
Positive and Negative Thoughts and Feelings Cannot Coexist
A common misconception about suggesting positivity is that that means suppressing negative thoughts and emotions. This is not true – after a tragic event, it is good to feel optimism in addition to despair or other negative emotions.
Positive and Negative States are Symmetrical and Opposite in Their Effects
This is untrue, in that negative and positive effect can have a similar, asymmetric, or symmetric impact.  This is important because negative effect is often used as the control group in studies, when in fact a neutral effect should be used. For example, if the impact is similar (and not symmetric), then having a positive effect will appear to have no effect.
Positive States are Trivial Niceties, Incapable of Creating Any Lasting Benefit
Again, this is untrue. Positive states have beneficial short-term AND long-term health impacts.
Prescriptions against serious pitfalls
The authors finish their review by commenting against the growing practice of going overboard – of recommending that people close of their minds against negative thoughts, and of shaming those with illness, claiming that it's their fault for not being positive enough. This goes without saying – this is a massive overextension of the research, more likely to cause harm than gain.
Positive Psychology Citations
The Value of Positive Psychology for Health Psychology: Progress and Pitfalls in Examining the Relation of Positive Phenomena to Health. Lisa G. Aspinwall & Richard G. Tedeschi. 21 January 2010. The Society of Behavioral Medicine 2010.