What would be the most common illnesses that have similar symptoms to schizophrenia?

Other psychoses, dep: The 'positive' symptoms of schizophrenia (voices, delusions) are also seen in severe mania, drug intoxications (esp hallucinogens), in delirium, some brain injuries, some drug & alcohol withdrawal states, & in several other medical conditions. The 'negative' symptoms (social withdrawal, poor hygiene, lack of emotion) are also seen in severe depression, and some brain & metabolic conditions.