Schizophrenia, perhaps the prototypical mental illness, is connected to stressors growing up, researchers say. Scientists at Johns Hopkins have found that stress hormones in mice seem to affect brain development in individuals who are susceptible based on genetics. In these individuals, the hormones can lead to the changes associated with schizophrenia. The scientists believe the same effects are likely to be found in humans.
People with schizophrenia—a collective term for a group of closely related disorders—perceive reality abnormally. It affects the brain and the central nervous system, according to neuroimaging studies. Schizophrenia has different types of symptoms. The familiar delusions and hallucinations, and similar symptoms, are called positive symptoms, things found in schizophrenia but not the general population. Schizophrenics also typically show what are referred to as negative symptoms, areas in which schizophrenics show a deficiency, such as social withdrawal, apparent emotionlessness, lack of motivation, and lack of attention to hygiene. The third kind are cognitive symptoms, such as unusual inattentiveness, or trouble understanding, processing, or remembering information.
In the Johns Hopkins study, researchers induces stress in mice by isolating them during a key period of their mental development, equivalent to human adolescence. In most of the mice, this had little effect in the long term. However, in mice bred to have a genetic predisposition to mental illness-like symptoms, the isolation produced those symptoms. Moreover, the mice persisted in the behaviors characteristic of mouse mental illness even when reunited with their peers, meaning the isolation produced permanent changes.
The team speculated that social isolation and stressful circumstances in human teenagers have similar effects on people predisposed to mental illness. Another risk factor for schizophrenia is prenatal exposure to certain toxins. Malnutrition and some viruses can also lead to schizophrenic symptoms. Because of the genetic factor, people with a family history are especially likely to be subject to the condition.