Other Mental Disorders with Similarities to Schizophrenia
There are at least five other disorders whose symptoms superficially might look like schizophrenia. Two are psychotic disorders. The others belong to an entirely different classification of mental illness: personality disorders.
Other Psychotic Disorders
Substance-induced psychotic disorder is the result of exposure to a drug or a toxin. The drug can be legal or illegal, prescription or nonprescription. As long as it is directly responsible for delusions and/or hallucinations, it qualifies as a cause of this disorder.
Psychotic disorder not otherwise specified is a type of “remainder” diagnosis. Psychiatrists use it when psychotic symptoms do not satisfy the criteria for other types of psychotic disorders, when symptoms seem to contradict each other, or when there is simply not enough information to fit a person's illness into one of the diagnostic categories.
Personality disorders differ from psychotic disorders. While the dominant feature of psychotic disorders is the presence of hallucinations or delusions, the defining feature of the following personality disorders is the presence of inflexible personality traits that make it difficult for people to interact successfully with others. These individuals may appear odd to others and are often anxious and unhappy. The three personality disorders that might be related to schizophrenia or other psychotic disorders are paranoid, schizoid, and schizotypal.
Paranoid Personality Disorder
People with paranoid personalities are distrustful and suspicious of others. They routinely believe other people are trying to take advantage of them, deceive them, or harm them. These traits begin to appear in childhood, adolescence, or early adulthood and may affect more men than women.
Some studies hint at a link between this personality disorder and psychotic disorders, including schizophrenia and the persecutory type of delusional disorder. This type of personality disorder may appear more often in relatives of patients with these psychotic disorders.
Schizoid Personality Disorder
Social detachment is the most obvious feature of this relatively rare disorder. It is accompanied by a noticeable lack of emotional expression. Sex drive is absent or very weak.
There is some indication that this disorder shows up more often in relatives of people with schizophrenia. Its effect in children and teens is similar to that of paranoid personality disorder.
There are, of course, many people who prefer solitude and are considered loners by their peers, but these preferences alone do not qualify as a personality disorder. Only when traits such as these are rigidly maintained and cause problems for the person do they qualify as potential personality disorders.
People with schizoid personality disorder are cut off from companionship and make no effort to connect to others. The lack of interest in others can even extend to family members. Patients prefer solitude. Their work and hobbies often reflect this preference.
Schizotypal Personality Disorder
Like schizoid personality disorder, schizotypal personality disorder is not often seen in mental health clinics, although approximately 3 percent of the population is estimated to have the disorder — three times the number of people with schizophrenia. If this is accurate, many people with this disorder are able to function without coming to the attention of the mental health care community. Few go on to develop schizophrenia.
People with this disorder have trouble with personal relationships. They aren't comfortable with them and they aren't good at keeping them. Another symptom is what psychiatrists call “perceptual disturbances.” These are not hallucinations as much as they are a sense that something is happening when in reality it is not.
People with schizoid personalities may have strange thought patterns that make them attribute significance to mundane occurrences. Another symptom of this disorder is belief in strange, paranormal, mystical, or magical phenomena. The disorder tends to run in families. It also occurs more often in relatives of people with schizophrenia.