Psychiatry has increasingly emphasized a biological basis for the causes of mental illness. Studies suggest a genetic influence in some mental illnesses, such as schizophrenia and bipolar disorder, although the evidence is not conclusive.
Magnetic resonance imaging (MRI) reveals structural differences between a normal adult brain, left, and the brain of a person with schizophrenia, right. The schizophrenic brain has enlarged ventricles (fluid-filled cavities), shown in light gray. However, not all people with schizophrenia show this abnormality. (Biological Perspective, Mental Illness)
Scientists have identified a number of neurotransmitters, or chemical substances that enable brain cells to communicate with each other, that appear important in regulating a personís emotions and behavior. These include dopamine, serotonin, norepinephrine (see epinephrine), gamma-amino butyric acid (GABA), and acetylcholine. Excesses and deficiencies in levels of these neurotransmitters have been associated with depression, anxiety, and schizophrenia, but scientists have yet to determine the exact mechanisms involved. (Biological Perspective, Mental Illness)
Advances in brain imaging techniques, such as magnetic resonance imaging (MRI) and positron emission tomography (PET), have enabled scientists to study the role of brain structure in mental illness. Some studies have revealed structural brain abnormalities in certain mental illnesses. For example, some people with schizophrenia have enlarged brain ventricles (cavities in the brain that contain cerebrospinal fluid). However, this may be a result of schizophrenia rather than a cause, and not all people with schizophrenia show this abnormality. (Biological Perspective, Mental Illness)
A variety of medical conditions can cause mental illness. Brain damage and strokes can cause loss of memory, impaired concentration and speech, and unusual changes in behavior. In addition, brain tumors, if left to grow, can cause psychosis and personality changes. Other possible biological factors in mental illness include an imbalance of hormones, deficiencies in diet, and infections from viruses. (Biological Perspective, Mental Illness)