Understanding Depression: An Interplay of Culture and Biology

Although both sexes suffer from depression, women are more likely to suffer from depression and in fact, women are twice as likely as men to develop major depressive disorder (MDD) (Guilloux et al. 2012). This sex difference is not unique to the United States but has been observed across countries ranging from high to low gender equity and economic development (Hopcroft and Bradley 2007). Researchers have continued to search for a biological mechanism that can explain a potential predisposition for depression in women but a consensus has yet to be reached. This failure to identify such a cause might be due in part to the potential existence of multiple factors. Furthermore, one may not be able to explain depression solely from a biological perspective; evidence suggests that cultural studies of depression are also important in understanding the disorder. A sociological position on illness could therefore also prove useful.

GABA interneuron related peptides, like neuropeptide Y (NPY), and other signaling molecules in the brain are among the possible genetic factors linked to a predisposition to depression. NPY, a neurotransmitter found in the brain and autonomic nervous system is thought to play a role in anxiety and stress, blood pressure, and fat storage (Gilloux et al 2012; Zhou et al. 2008). A study by Gilloux et al. (2012) focused on a section of the amygdala, a brain structure, which is associated with the regulation of emotion. In post-mortem evaluations of subjects with major depressive disorder, all of who were female, they noted a significant downregulation for the genes that encode for these signaling molecules such as NPY. With evidence that these peptides might play a role in MDD, they then looked to mouse models of depression. In their experiments, they found a similar decreased function of NPY (Gilloux et al. 2012). Thus, lower levels of NPY and related GABA neuron peptides could lead to a greater chance of developing depression. Finally, they compared these observations with similar work previously performed in male mice. This earlier study showed a less pronounced downregulation of the genes of interest, resulting in higher levels of NPY, which might help to explain this sex difference between males and females.

However, as already noted, this biological explanation might not be sufficient in understanding this unequal distribution. Other factors, such as socioeconomic status and even cultural factors within the home, also seem to play a large role in one’s chance of developing depression. These cultural forces are likely to affect one’s stress and anxiety, which could, in turn trigger depression. One study performed by Hopcraft and Bradley surveyed males and females across 29 countries on matters such as employment, marriage status, self efficacy and religion, which can all impact one’s mental wellness. In all countries, they noted that females were significantly more depressed than males (Hopcraft and Bradley 2007). To compare between groups of females, they examined each country’s Gender-related Development Index (GDI). GDI is a measurement of gender gap in regards to health, education and command of economic resources. As the study found, those in countries with a high GDI, were less likely to be depressed than those in countries with a low GDI.

Fig 1. Probability of depression by age and sex. Men and women are grouped by high or low GDI.

As the graph shows, men in countries with a high GDI were less depressed than men in countries with a low GDI. Research has suggested that everyday life is more taxing in less developed societies due to the greater threat of war, poverty, disease and social unrest to explain this phenomena. Both groups of males, however, fell below female scores for depression. Some researchers propose that males benefit from their social standing in society, resulting in the gender gap. While females may find themselves impacted from the same issues of disease and social unrest as men, males still find that they have greater self efficacy and freedom of choice, which would improve their quality of life (Hopcraft and Bradley 2007; Rosenfield 1980).

Ultimately, it is difficult to say which plays a greater role in this sex difference in depression – cultural or biological factors. Although it is appealing to pinpoint a particular biological pathway to treat, it is likely the case that society and biology are both pertinent and so neither can be discounted when considering the issue.

References

Guilloux J, Douillard-Guilloux G, Kota R, Wang X, Gardier AM et al. (2012). Molecular evidence for BDNF- and GABA-related dysfunctions in the amygdala of female subjects with major depression. Molecular Psychiatry 17: 1130-1142

Hopcraft RL and Bradley DB. (2007). The sex difference in depression across 29 countries. Social Forces 85(4): 1483-1507.

Rosenfield S. (1980). Sex differences in depression: do women always have higher rates? Journal of  Health and Social Behavior 21(1): 33-42.

Zhou Z, Zhu G, Hariri AR, Enoch M, Scott D et al. (2008). Genetic variation in human NPY expression affects stress response and emotion. Nature 452: 997-1002.