Hallucinations and delusions: These are two of the most common symptoms of schizophrenia, especially when paranoia is present. Hallucinations may involve sight, hearing, touch, taste or smell (e.g. a person insists he or she sees or smells something that does not exist). Hallucinations are most often “auditory” in nature and involve hearing one or more voices — even though no one else is present or actually talking. The voices may give commands, comment on the individual’s actions or say harsh, hurtful things. Command hallucinations can be dangerous if the voices are instructing the person to hurt him or herself or others.1,3,5
Delusions involve a firmly and persistently held belief that is not realistic, true or feasible. Delusions may be bizarre (e.g. the belief one’s brain has been surgically removed and replaced with an alien brain) or non-bizarre (e.g. a woman insists she is pregnant despite medical proof she is not).1,3,5
Disorganized behavior: This may manifest in thoughts, speech and/or behavior. Someone with disorganized speech may frequently jump from one topic to the next, say things with no relevance to the current conversation or speak complete gibberish. In order to qualify as a symptom of schizophrenia, disorganized speech must be severe enough to interfere with the ability to communicate.1,3,5
Catatonic behavior: Some individuals with schizophrenia become catatonic. This can manifest as extreme obliviousness to one’s surroundings (stupor), a rigid stance or bizarre posture, resistance to being moved or being told to move or excessive, excited movement that serves no purpose.1,3,5
Negative symptoms: Often confused with clinical depression, these symptoms include a lack of emotional expression, speaking in a dull, limited or disconnected manner (alogia) and an inability to initiate and follow through with tasks (avolition).