Most schizophrenia of the simple type begins slowly in adolescence with no apparent cause, has a long course, continues to progress, and rarely remits spontaneously; early symptoms of neurasthenia-like illness may occur. The main clinical manifestations are increasing isolation, passivity, laziness, loss of interest, emotional indifference and erratic behavior. Because psychotic symptoms such as delusions and hallucinations are not obvious, they are often not easily detected at an early stage and are generally not well treated. With the prolongation of the disease, behavioral withdrawal, emotional indifference, impoverished thinking and weakened will gradually worsen, leading to serious deficits in social functioning. Early detection and treatment can lead to improvement of certain symptoms.