There are some really interesting articles written by Andres Ruiz on Medium here he compares the biomedical model to the biopsychosocial model. From what I understand, the biomedical model puts its emphasis on biochemical processes being the reason for mental illness, removing environmental factors, such as small-scale or large-scale social interactions.

It's all pretty interesting. Then there is epigenetics which from what I've found states that environmental stressors impact genetic structures. For instance, with holocaust survivors, their progenies are more susceptible to experiencing PTSD because their ancestors experienced the horror of long-term, sustained stress(i.e. being in fight/flight/freeze for extended periods of time), which altered them genetically.

Is it as simple as the biological and chemical processes occurring within an individual? Seems to not be. I've wondered why mental illness, especially depression, bipolar, or schizophrenia have been around for 1000s of years and there hasn't been a cure, or even an established etiology. Even if a cure were developed or the etiology uncovered, considering that social influences can alter your genetic makeup, isn't it possible that the zeitgeist would beget other/novel, if not the same, mental illnesses? Seems like it's some kind of feedback system.