Thoughts on week 9: mental illness

This week we talked about mental disorders and specifically about anxiety disorders and depression and their hypothesized biological mechanisms. The monoamine theory of depression is  very well known and seems to have had some promising support in the 20th century but has been outdated by new theories. I’m familiar with the plasticity enhancing hypothesis of SSRI’s which is supported by plasticity inducing theory of classical psychedelics and its possible implications in depression treatment.

The diathesis-stress hypothesis of mood disorders was somewhat new and somewhat familiar to me. It states that changes in HPA axis are the main biological basis for mood disorders which I understand as stress being the main biological cause of mood disorders. This is something that I have been thinking since my bachelor studies in nutrition. I might expand it to be the cause of all chronic disease. According to this theory HPA axis activity is important for mood disorder development and is affected by genetic traits and features of the environment, especially stressful experiences in the early stages of life. The hypothesis is supported with findings that HPA axis is hyperactive in severely depressed patients and that there’s decrease in glucocorticoid receptors in MDD patient’s hippocampus. Hippocampus has been shown to be able to regulate stress response by feedback regulation from the activation of hippocampal glucocorticoid receptors. In chronic stress hippocampal cells die which might be one underlying cause for both anxiety and depression. The idea that SSRI’s effect could come from increase in glucocorticoid receptors in the hippocampus was new and intriguing to me. The studies of grooming’s effect on rat/mice pup’s glucocorticoid receptors was familiar to me and it seems quite obvious that an infant that receives caring and soothing touch especially in a stressful situation is programmed to be less stressed. But there might be a caveat of too much care having possibly even opposing effect.