There is still a big role for psychosocial treatment:

That which makes us clever, makes us mad:

From The Times OnLine, by Mark Henderson, Science Editor
http://www.timesonline.co.uk/tol/news/uk/science/article1355884.ece
" One of the most devastating types of mental illness could be a by-product of the evolution of human beings’ uniquely sophisticated intelligence, a new genetic study has suggested.
Scientists have discovered that a common version of a particular gene appears both to enhance a key thinking circuit in the brain, and to be linked to a raised risk of schizophrenia."

Major mental disorders appear more clearly to be biological in origin
The genetic basis of major mental disorders is increasingly clarified, although no one study can be assumed to have a final word. I have personally seen reports of many differing studies, with different areas on the genome found to underlie bipolar disorder which is among the most heritable mental disorders, more than schizophrenia, and up there with ADHD. Same goes with unipolar depression although that has been found to have a lower concordance rate. Still, major mental disorders all seem to be biological in etiology, and when people speak of the environmental piece, they often neglect to mention that the most important environmental factors also seem to be what we might consider "physical" or "biological' in origin. For example, OCD, a highly heritable disorder, is not infrequently set off in children following a strep infection. The strep bacteria apparently releases a neurotoxin, which in vulnerable children, leads to brain inflammation and whatever other local trauma which then leads to OCD. Neurotoxins are also found increasingly to be associated with severe mental disorders. So it is important that we make it clear when we speak of environmental factors that we include exposure to pathogens and to neurotoxic agents. It is almost impossible today, from my reading anyway, to determine what neurotoxin is contributing to what, because neurotoxins don't come in "single neurotoxic" packages. In heavily polluted areas, the neurotoxins are multiple, and no one has really studied the effects of multiple interacting neurotoxins on the brain, to say nothing of the embryonic brain, or the young developing brain.

Some psychologists are worried, "are we out of work?"
I think some psychologists worry as things become more clearly biological, thinking we will be out of work. Nothing could be further from the truth. I doesn't matter what the etiology of a serious mental disorder is, psychological treatment is often essential for a good prognosis, along with psychopharmacological treatment in some cases, and other types of psychosocial treatments as well. Consider the problems that confront a child with ADHD. They are disliked by their peers, they have difficulty in school, all of which amounts to serious failure for the child. Thus ADHD may be entirely biological in etiology, but the person with ADHD has dealt with so many difficulties as the result of their illness, they need and deserve psychological help.

What about addiction?
Consider addiction. A person with addiction disease may have been prone to addiction because of heritable factors, and may have been environmentally triggered by neurotoxins, or multiple neurotoxins. But the treatment is abstinence from mind altering drugs, and often this is only possible with the support of a psychologist or other mental health professional. People with this disease need and deserve a great deal of psychosocial support as they find in programs like AA, and the individual kind of support they get in psychotherapy.

Along with illness comes a whole package of psychosocial insults
People with all "biological" illnesses whether they are "mental illnesses" or "other physical illnesses" often suffer from numerous psychological insults, stigma, increased daily life stressors as they monitor their illnesses, the need to take multiple medications, the list goes on and on. It doesn't matter if the etiology is all biological, the treatment often has to include a psychosocial component for the best prognosis and outcome. So for those who worry that the growing knowledge of the biological nature of mental disorders means we are out of work, worry no more. We just have to be ready to help people as they struggle to recognize, deal with, get treatment for their biologically based disorders. There is a great deal of work for us, perhaps more than ever as the importance of solid psychological support is recognized as an essential component of treatment for all illnesses.