Biological psychologists explain behaviors in neurological terms, i.e., the physiology and structure of the brain and how this influences behavior. Many biological psychologists have concentrated on abnormal behavior and have tried to explain it. For example, biological psychologists believe that schizophrenia is affected by levels of dopamine (a neurotransmitter).
This perspective has helped psychiatry take off and help relieve the symptoms of the mental illness through drugs and to a lesser degree nutrition. However, other disciplines would argue that this just treats the symptoms and not the cause. This is where health psychologists use the finding that biological psychologists produce and look at the environmental factors that are involved to get a more holistic picture.