Atypical antipsychotics are a class of medications used to treat mental health conditions such as schizophrenia, bipolar disorder, and major depressive disorder. They are called atypical because they are different from the older, typical antipsychotics in that they have fewer side effects and are more effective in treating the symptoms of mental illness. Atypical antipsychotics work by blocking certain receptors in the brain that are involved in the regulation of mood and behavior.