Depression – cause or effect of obesity?

Obesity is an important public health problem, both because of the steady increase in its prevalence and the cost of treating its complications. In recent years, increasing attention has been paid to the psychological effects of obesity, such as lowered self-esteem, lack of acceptance of one’s appearance and social isolation. On the one hand, these psychological problems may be the cause of increased stress levels, lowered mood and the occurrence of depression, while on the other hand, chronic stress, lowered mood and the occurrence of depression, as well as associated changes in eating behavior, such as comfort eating and compulsive eating, may be responsible for the development of obesity.

However, regardless of which of these diseases is the cause and which is the effect, their co-occurrence may lead to an increase in mortality, as both obesity and depression are independent risk factors for cardiovascular disease. So is there any correlation between obesity and depression?

• Obesity and depression are diseases that lead to many health complications. Based on previous studies, both diseases have been shown to be independent risk factors for the development of coronary heart disease and increased mortality.
• Increasing attention is being paid to the psychological effects of obesity, such as lowered self-esteem, lack of acceptance of one’s appearance and social isolation. On the one hand, these psychological problems can cause increased stress levels, lowered mood and the onset of depression. On the other hand, chronic stress, lowered mood and the occurrence of depression, as well as associated changes in eating behavior, such as comfort eating and compulsive eating, may be responsible for the development of obesity. These observations formed the basis for the theory of the so-called “bidirectional” relationship between obesity and depression. Due to the clinical and epidemiological importance of the co-occurrence of obesity and depression, studies have been conducted for years on the physiological links between these diseases and the influence of various factors on their development.
• Prevalence of co-occurrence of obesity and depression – Previous studies on the prevalence of depression in obese people have yielded contradictory results – some have shown an increased prevalence, while others have found a lower or normal prevalence. It seems that the results obtained largely depended on the diagnostic criteria adopted for depression and the population studied.
• In both obesity and depression, abnormalities in the secretion of neurotransmitters such as serotonin, norepinephrine, dopamine and neuropeptide Y, involved in the regulation of eating behavior and mood, are observed. A reduction in the number of serotonergic receptors in the brain and an impaired serotonin response have been observed in depressed individuals. Reduced serotonin sensitivity has also been observed in obesity.
• The role of pro-inflammatory cytokines in the development of depression has been studied for several years. Levine et al, analyzing the cerebrospinal fluid of severely depressed subjects, observed increased levels of interleukin 1 (IL-1, interleukin 1), decreased levels of interleukin 6 (IL-6, interleukin 6) and no differences in tumor necrosis factor a (TNF-a, tumor necrosis factor a) compared to controls. In addition, they found a positive correlation between the severity of depression and the concentration of IL-1 in cerebrospinal fluid. Based on the results of previous studies, it is reasonable to believe that chronic stress may be the cause of increased inflammatory activation, which may play a role in the pathogenesis of depression. Increased inflammatory activation is also observed in obese individuals, in whom adipose tissue is a source of pro-inflammatory cytokines, as reflected by an increase in serum IL-6 and TNF-a. Therefore, it seems that increased inflammatory activation may represent another link between the pathogenesis of obesity and depression.
• In the clinical picture of both diseases, changes in appetite, disordered eating behavior and changes in physical activity are observed. People with depression show both decreased and no changes and increases in appetite. Based on their study, Weissenburger et al. showed that weight gain due to increased appetite and decreased physical activity occurs in about 40% of depressed subjects, while weight reduction occurs in 30%.

In conclusion, it can be said that despite common pathophysiological pathways and similar external factors influencing the development of obesity and depression, the question posed in the title as to which of these diseases is the cause and which is the effect cannot be clearly answered. It seems that in individual cases, the interview with the patient may be conclusive.

It should also be emphasized that regardless of which of these diseases is the cause and which is the effect, their co-occurrence may lead to increased mortality, since both obesity and depression are independent risk factors for cardiovascular disease. Depression accompanying obesity can also be a cause of weight loss treatment failure. Therefore, it is important to keep in mind the frequent co-occurrence of obesity and depressive disorders and the need for their simultaneous treatment, as well as the important role of psychotherapy in the treatment of both disorders.

Based on a research paper by Magdalena Olszanecka-Glinianowicz

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