Other forms: psychiatrically
The adjective psychiatric is good for describing things related to mental illness and its treatment.
Use psychiatric when you're talking about the medical specialty that helps people with emotional or mental disorders. You could talk about a psychiatric nurse, a psychiatric hospital, or psychiatric drugs, for example. Any time you see a word that begins with psych you can be sure it has to do with the mind, since psykhe is "mind" in Greek. The suffix iatreia means "healing or care."