Diet, Stress and Mental Health

Abstract

Introduction: There has long been an interest in the effects of diet on mental health, and the interaction of the two with stress; however, the nature of these relationships is not well understood. Although associations between diet, obesity and the related metabolic syndrome (MetS), stress, and mental disorders exist, causal pathways have not been established.

Methods: We reviewed the literature on the relationship between diet, stress, obesity and psychiatric disorders related to stress.

Results: Diet and obesity can affect mood through direct effects, or stress-related mental disorders could lead to changes in diet habits that affect weight. Alternatively, common factors such as stress or predisposition could lead to both obesity and stress-related mental disorders, such as depression and posttraumatic stress disorder (PTSD). Specific aspects of diet can lead to acute changes in mood as well as stimulate inflammation, which has led to efforts to assess polyunsaturated fats (PUFA) as a treatment for depression. Bidirectional relationships between these different factors are also likely. Finally, there has been increased attention recently on the relationship between the gut and the brain, with the realization that the gut microbiome has an influence on brain function and probably also mood and behavior, introducing another way diet can influence mental health and disorders. Brain areas and neurotransmitters and neuropeptides that are involved in both mood and appetite likely play a role in mediating this relationship.

Conclusions: Understanding the relationship between diet, stress and mood and behavior could have important implications for the treatment of both stress-related mental disorders and obesity.

Keywords: Mediterranean diet; brain; cardiovascular disease; child abuse; coronary artery disease; depressive disorder; diet; galanin; ghrelin; metabolic syndrome; microbiome; myocardial ischemia; nutrition; obesity; posttraumatic; serotonin; somatostatin; stress disorders.

Figure 1

The complex relationship between diet, obesity and behavior. Stress acts through the brain to both affect eating and exercise behaviors (Path A) and stress-related psychiatric disorders including posttraumatic stress disorder (PTSD) and depression (Path B), both of which can lead to changes in metabolism, metabolic syndrome (MetS) and obesity (Paths A and B). Binary relationships also exist between unhealthy eating and PTSD/depression and the brain (i.e., both in turn lead to changes in brain function). Unhealthy eating can result in diets high in saturated fat (fatty food ingestion) (Path A) that can affect mood (dysphoria) as well as leakiness of the intestinal wall (Path A), which can lead to changes in the gut microbiome which modulate obesity, MetS and metabolism (Path A), as well as feeding back on the brain (Path A) to influence mood (dysphoria). Physical disorders including cardiovascular disease (CVD) and diabetes (Path C) and physical factors such as intra-abdominal fat (Path C) are affected by stress and related to PTSD and depression. A complex system of neurotransmitters (norepinephrine, serotonin, dopamine) (Path D), inflammatory markers (Path E) and neuropeptides (ghrelin, somatostatin, galanin) (Path F) present in the gut and brain are also influenced by stress via the brain, influence the gut microbiota and physical disorders and factors in a binary fashion and in turn regulate both feeding behavior and psychiatric disorders. Within the figure, the line color indicates the path, with dashed lines indicating primary pathways and solid lines indicating secondary pathways.