A study of factors associated with post-traumatic stress disorder (PTSD) has led to a number of novel findings linking nutrition to experiences of PTSD. Notable among them is the discovery that Canadians, between the ages of 45 and 85, were less likely to exhibit PTSD if they consumed an average of two to three fiber sources daily.
“It is possible that optimal levels of dietary fiber have some type of mental health-related protective effect,” says Karen Davison, Director of the Nutrition Informatics Research Group and Health Science Program Faculty Member at Kwantlen Polytechnic University.
“This may be due to the communication network that connects the gut and brain via short chain fatty acids (SCFAs), which are metabolic byproducts of bacterial fermentation made by microbes in the human gut.”
“Produced from fermenting fiber in the colon, SCFA molecules can communicate with cells and may affect brain function,” Davison says.
Other diet-related factors found to be associated with an increased likelihood of PTSD included daily consumption of pastries, pulses and nuts, or chocolate.
“This finding that increased intakes of pulses and nuts were associated with increased odds of PTSD was unexpected,” states Christina Hyland, a doctoral student at the University of Toronto’s FIFSW. “However, the measures for these in the Canadian Longitudinal Study on Aging dataset included sources such as peanut butter, and may have also included less healthy variations such as salted or candied nuts.”
The study team analyzed data from the baseline Canadian Longitudinal Study on Aging, which included 27,211 participants aged 45-85 years, of whom 1,323 had PTSD.
The study also found relationships between PTSD and factors such as poverty, gender, age, immigration history, ethnicity, marital status and physical health.
Poverty was strongly associated with PTSD, with one in every seven respondents whose household income was under $20,000 per year experiencing the disorder.
“Unfortunately, we do not know whether PTSD symptoms undermined an individual’s ability to work, which resulted in poverty or whether the stress associated with poverty exacerbated PTSD symptoms in respondents,” says senior author, Esme Fuller-Thomson, director of the Institute for Life Course & Aging and professor at the University of Toronto’s Factor-Inwentash Faculty of Social Work (FIFSW) and Department of Family & Community Medicine.
Women had almost double the prevalence of PTSD in comparison to men (6.9% versus 3.9%). And those who were widowed or divorced were twice as likely to experience the disorder compared to those who were married or living common-law (8.8% versus 4.4%).
When it came to age, the prevalence of PTSD was highest for those 45 to 54 years old (6.4%) and lowest for those aged 75 and older (3.1%).
“This supports previous research, which found that PTSD tends to be most common among men in their early 40s and women in their early 50s,” says co-author, Karen Kobayashi, Professor in the Department of Sociology and a Research Fellow at the Institute on Aging & Lifelong Health at the University of Victoria.
The prevalence of PTSD was higher among individuals who had at least two health conditions, who were experiencing chronic pain, or who had a history of smoking.
“This is consistent with results from other studies, which found increased risks of cardiovascular, metabolic, and musculoskeletal conditions among individuals with PTSD,” states co-author Meghan West, a Master of Social Work student at the U of T’s FIFSW.
“These links may be due to alterations in the hypothalamic-pituitary-adrenal axis (HPA axis), sympathetic nervous system inflammation, or health behaviours that increase the risk of poor physical health.”
The prevalence of PTSD among visible minority immigrants (7.5%) was more than double that of white immigrants (3.6%) and approximately 50% higher than whites born in Canada (5.6%).
“Our findings underline the importance of considering race and immigration status separately,” states co-author Hongmei Tong, Assistant Professor of Social Work at MacEwan University in Edmonton.
“Visible minority immigrants in Canada are largely from South Asia, China, and the Middle East, where groups of individuals have experienced political conflict and/or disruption during the previous 60 years,” he says.
“Immigrants from these regions are also more likely to have experienced traumatic incidents such as natural disasters and armed conflict, and could be at greater risk of PTSD as a result. As such, there may be a greater need for mental health resources for visible minority immigrants.”
The results of this study were published this week in Social Psychiatry and Psychiatric Epidemiology, an international medical journal that focuses on the epidemiology of psychiatric disorders.
The relationship between diet and behavior has long been a topic of interest. This includes the effects of diet on both mental and physical health, as well as related topics of the role of stress and obesity in these processes . Dietary modification can prevent the development of cardiovascular disease (CVD) and diabetes , and stress-related mental disorders, including major depression and posttraumatic stress disorder (PTSD), are associated with an increased risk for CVD [3,4,5,6,7,8], although the mechanisms of these interactions are not well understood [9,10].
Specifically, there is a limited understanding of how diet affects mental health, and the way outcomes of unhealthy diet such as obesity interact with stress-related psychiatric disorders.
The relationship between these factors is often bidirectional. For example, changes in diet may influence psychiatric disorders through direct effects on mood, while the development of psychiatric disorders can lead to changes in eating habits . Figure 1 shows the myriad and complex relationships that can exist between diet and psychiatric symptoms.
In Path A in the figure, stress can act through the brain to cause an increase in over-eating , including binge-eating , and a reduction in exercise that in turn leads to obesity and/or metabolic syndrome (MetS, defined as increased blood pressure, and blood sugar, excess waist body fat and elevated cholesterol or triglyceride levels), which may in turn lead to disorders such as depression due to functional and/or social impairments .
In Path B, stress-related psychiatric disorders develop (PTSD, depression) that are associated with changes in metabolism and obesity . Path C acts through physical disorders such as cardiovascular disease (CVD) and diabetes, that may come by way of PTSD and depression, and are related to those disorders in a bidirectional relationship or perhaps through shared pathways.
Stress-induced over-eating leads to obesity, which in turn can be associated with changes in neurotransmitters, neuropeptides, and inflammatory factors that are present in both the gut and the brain and have effects on both mood and subsequent eating behaviors [16,17].
Path D shows the effects of neurotransmitters (e.g., serotonin) and neurohormones (cortisol), inflammatory factors are shown in Path E, and neuropeptides (ghrelin, galanin) reviewed below are shown in Path F. Finally, returning to Path A, changes in diet can affect the gut microbiome, which can have effects on mood, and is involved in a complicated bidirectional interaction between brain and inflammatory function as well as the abovementioned neurotransmitters and neuropeptides .
This paper reviews possible mechanisms by which diet and obesity can affect mental health and the brain, and the complex interplay between these different factors. We review the effects of diet on mood, with feelings of dysphoria or symptoms of depression most relevant within this context.
Factors such as ingestion of fatty foods, as reviewed below, may impact feelings of dysphoria, which is relevant to the topic. Many studies reviewed below examined depressive symptoms in populations that are not suffering from psychiatric disorders, such as pregnant women, or looked at populations such as the elderly in the community at risk for nutritional deficiencies.
These studies of depressive symptoms are to be differentiated from studies of populations that meet the criteria for major depression, which together with PTSD are more relevant to the practice of clinical psychiatry. Another relevant topic to effects of diet on mental health is the area of supplements and specific food products, including polyunsaturated fats (PUFAs), which have been the subject of a variety of clinical trials as both treatments and preventative agents for depression.
More information: Social Psychiatry and Psychiatric Epidemiology, DOI: 10.1007/s00127-020-02003-7