Schizophrenia Spectrum Disorders

Schizophrenia symptoms split into two camps. Positive symptoms add something to behavior that shouldn't be there: hallucinations, delusions, disorganized speech, and catatonia. Negative symptoms subtract something that should be there: flat affect, loss of motivation, social withdrawal, reduced speech. A hallucination is a false sensory experience with no outside stimulus, most often hearing voices. A delusion is a false belief held with total conviction despite clear evidence against it, like being certain the government is tracking you through the television. Disorganized speech shows up as loose associations, jumping between unrelated ideas without logical connection. Catatonia means the body gets stuck: immobility, odd postures held for hours, or excessive purposeless movement. The brain treats an internally generated thought or sound as if it arrived from outside, and the person has no built-in way to doubt that certainty, which is why a hallucinated voice feels as real as a knock on the door.

The dopamine hypothesis explains the positive symptoms through neurotransmitter activity. It proposes that overactive dopamine transmission in certain brain pathways drives hallucinations and delusions. Evidence comes from two directions: antipsychotic drugs that block dopamine receptors reduce these symptoms, while amphetamines and other dopamine-boosting drugs can produce hallucinations and delusions in people who never had schizophrenia. Neither finding proves dopamine causes the disorder alone, but together they point to dopamine as a key piece.

Schizophrenia sits in this unit alongside other disorders precisely because it gets confused with one of them: dissociative identity disorder. Risk for schizophrenia also illustrates the diathesis-stress model that runs through the whole unit. A genetic vulnerability by itself often stays silent. Add a prenatal stressor, like a mother's viral infection during a critical window of fetal brain development, and the odds of the disorder emerging rise sharply. Genes load the gun; environmental insult can pull the trigger.