→ Main article: Symptoms and diagnosis of schizophrenia
The symptoms of schizophrenia are traditionally divided into two broad areas: Positive symptoms and Negative symptoms. More recently, however, the cognitive symptoms of the disorder have also received increasing attention and are seen as a separate third domain.
Contrary to what the term suggests, however, it does not refer to intelligence deficits, but to problems with attention, memory, and action planning, among other things. The extent to which these areas are affected best predicts how well patients can cope with everyday life. Cognitive disturbances of this type are a central symptom complex of schizophrenia. Thinking may become short-tempered, or multi-layered relationships may not be grasped in their complexity. Linguistic expression becomes impoverished. In exacerbated cases, perseveration (stereotyped repetition of a word or thought) or idiolalia (unintelligible sounds) may occur.
The severity of symptoms depends in part on the personality of the individual. The overall symptomatology differs greatly between different individuals; however, individual patients often retain their individual symptom pattern over long periods of time.
Positive symptoms
Positive symptoms (or plus symptoms) denote exaggerations of normal experience and are therefore regarded as a kind of "surplus" compared to the healthy state. These include strong misconceptions of the experienced reality up to hallucinations and loss of reality. Schizophrenias with predominantly positive symptoms often begin suddenly, and often there are no outwardly conspicuous features beforehand. The course of the disease is rather favourable in this case.
Characteristic positive symptoms are content-related thought disorders, ego disorders, sensory delusions and inner restlessness. Typical for the content-related thought disorders is the formation of a delusion. Auditory hallucinations (acoasms) are common: About 84% of people with schizophrenic psychosis perceive thoughts that they think their origin is external. For example, they perceive voices that, in rare cases, also give orders. This is referred to in common parlance as "hearing voices". Often those affected have the impression of being insulted by foreign voices. Such an experience may occur while alone or in the midst of sentences said by bystanders. Hallucination of voices also occurs in deaf people, even in those born deaf. However, in deaf persons with a diagnosis of schizophrenia, visual and tactile hallucinations are significantly more common (in about 50% of persons each) than in schizophrenia in general (about 15% and 5%, respectively).
Ego disorders include:
- Ideation: experiencing one's own thoughts as imposed by others
- Thought propagation: the idea that others could "eavesdrop" or "read" one's own thoughts
- Thought deprivation: sense of loss that others are stealing or cutting off one's thoughts.
- External control: Feeling of being controlled by others like a remote-controlled robot.
Negative symptoms
Negative symptoms (or minus symptoms) refer to limitations of normal experience as well as of mental functions that were previously present but are reduced or completely absent due to the disease. These symptoms thus represent a deficiency compared to the healthy state. The following table gives an overview of the negative symptoms:
| Negative symptom | Explanation |
| Affect flattening | Lack of range of emotions in perception, experience and expression. The impoverishment of emotions (affects) manifests itself in a reduced ability to "participate emotionally". The affected persons react emotionally only to a limited extent to normally moving events and appear to be little touched by pleasant or unpleasant events. The normal change between different affective states (joy, curiosity, sadness, anger, pride ...) is lost. |
| Alogie | Lack of verbal expression with delayed, wordy responses and poorly differentiated language. |
| Asociality | lack of sociability in the form of disinterest in socialising with others, social withdrawal, few friends and little sexual interest (not to be confused with anti-social behaviour) |
| Avolition | lack of ability to initiate and maintain goal-directed behaviour |
| Drive disorder | reduced ability and will for goal-oriented activity (lack of drive) |
| Abulie | Lack of willpower in the form of difficulty in making decisions |
| Apathy | lack of excitability and insensitivity to external stimuli, leading to apathy and lack of interest |
| Anhedonia | lack of capacity to feel pleasure or enjoyment |
| "dynamic draining" | Lack of motivation for activities with resulting lack of drive. Includes lack of future planning, up to extensive lack of perspective. |
| motor deficits | Lack of facial expression and gestures with reduced movement. These deficits often make the ill person appear aloof or out of touch. This distance can be bridged by attention, which is usually gratefully accepted by the ill person, even if they cannot show this through facial expressions and gestures. The impoverishment of psychomotor activity makes affective resonance appear more impaired than it is. Thus, if patients are not spoken to during a solidified delusional state, they are usually receptive to attention. |
Schizophrenia with pronounced negative symptoms often begins insidiously, and the course of the disease is rather unfavorable. Negative symptoms can occur months or years before the acute psychotic symptoms ("bend in the life curve", "preceding defect"). Very often, sleep disturbances and not infrequently depressive symptoms occur as early symptoms. The negative symptoms usually intensify or solidify with increasing duration of the illness.
In about two thirds of people suffering from schizophrenia, the negative symptoms outlast the positive symptoms after an acute episode ("schizophrenic defect", "residual state", "residual symptomatology"). These limitations, which vary in severity, lead to contact disorder, social withdrawal, and often disability. However, in a certain percentage of people with schizophrenia, no residual symptoms remain (see residual symptomatology).
After the acute phase of a relapsing schizophrenia has subsided, a temporary depressive episode ("depressive aftershock") occasionally follows. A distinction should be made between true negative symptoms and the side effects of therapy with a neuroleptic. The side effects of neuroleptics can be similar to negative symptoms.