What I have noticed is that the immune system is relevant to the nervous system. There is a rise in allergies, food sensitivities and environmental toxins. When you include the manipulation of the human immune system with changes in our food supply and lifestyle, you get mental illness.
It used to be considered "common knowledge" that mental illness was inherited. So people avoided marrying anyone with mental illness in their family. Then Freud made mental illness mostly about the emotional environment a child grew up in. It was based on a bunch of myths about the human psyche that was based on symbolism, dreams, wishful thinking and abstractions like Id and superego. I agree that symbolism and myth have a place in understanding the healthy human psyche. But I think mental health and illness have a very real biological component, that we ignore or minimize at our peril.
I think that physical injury can also cause mental illness. There is a large component of mental illness that relates to mild traumatic brain injury from falls and accidents. With people engaging in riskier sports, these are a big component. And most mild brain injuries are forgotten easily (it is a common thing to forget them unless repeatedly reminded.)
Many years ago, some doctors noted the effect of a strict vegetarian diet, and some other types of diet on schizophrenia. Now we know that the genes that code for schizophrenia are in the same section of DNA as immunity is.
The answer ultimately, in my opinion, isn't going to be an increasing amount of the use of heavy sedatives and other drugs. It will be assessing the functioning of the immune system and the lifestyle of the mentally ill person. It will also mean carefully modifying and refining our current methods of influencing the human immune system. It will also require an admission that there are very real neurological effects in some people caused by chemicals we use in food production, distribution and storage.
We also will need to deal with mental illness in a more effective way that supports the family and the community so that the family can function while the mentally ill person is part of it. Separating the mentally ill from family and society didn't work very well and permitted many abuses and not much real progress in treatment. But just putting the mentally ill out into the streets didn't do much for them, either.
The way things work currently, the family is left out of the loop of services without guardianship, until things get so bad that the mental illness is often irreversable with current treatments because of self-medication with alcohol and street drugs that cause further brain damage.