Definition
Schizophrenia is a pervasive, debilitating disease characterized by positive symptoms of hallucinations, delusions, and thought disorder (also referred to as psychosis), and negative symptoms of chronic social dilapidation. Emil Kraepelin first distinguished schizophrenia (then termed dementia praecox) from bipolar psychosis more than 100 years ago, by contrasting the long-term deteriorating course of delusions and hallucinations characteristic of schizophrenia to the intermittent course of bipolar illness. Schizophrenia remains a clinical diagnosis made on the basis of the individual’s psychiatric history and mental status examination, as no laboratory or imaging studies can validly diagnose it.
Schizophrenia is described in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders as two or more of the following symptoms active for a minimum of 1 month’s duration (unless adequately treated) as well as the continuing presence of a symptom for 6 months: delusions, hallucinations, disorganized speech, disorganized behavior, and negative symptoms along with a significant disturbance of the individual’s functioning that results in disturbances in occupation, social interaction, or the management of one’s self-care. These symptoms of schizophrenia can be characterized as either positive or negative.
The positive symptoms of schizophrenia consist of abnormalities of sensory experience and cognitive processing. These manifest as hallucinations, delusions, bizarre behavior, or formal thought disorder. Hallucinations are perceptions in the absence of physical stimuli. In schizophrenia, auditory hallucinations usually predominate, but, in patients with late-onset schizophrenia, olfactory, visual, tactile, or gustatory hallucinations may be present. In schizophrenia, the hallucinated voices are described as coming from outside the person’s head and providing a running commentary on the patient’s behavior. At times, these speak directly to the individual or converse with each other. Voices that tell the individual what to do are referred to as command hallucinations.
Delusions are fixed, false, idiosyncratic beliefs and consist of ideas and beliefs that are persecutory, bizarre, or grandiose. The idea that the person is being controlled by outside forces is common.
Bizarre behavior may be observed in the person’s appearance (odd/inappropriate layering of clothing) or in their aggressive, agitated or repetitive/stereotyped behavior (for example, flipping the light switch multiple times or repeated closing and opening the door). Formal thought disorder includes illogical or incoherent speech in the absence of aphasia. It manifests as tangentiality, loose associations (a lack of logical connection between sentences), or derailment (the sudden loss of train of thought).
The negative symptoms of schizophrenia result in a decline in the person’s baseline social, interpersonal, and volitional activity. People with schizophrenia often have a diminished range of facial expression, a phenomenon termed affective flattening; poor eye contact, and decreased expressive gesturing. Spontaneous speech decreases and speech latency increases. Individuals with schizophrenia become less social and form few close relationships with others. As the disease progresses, avolition and apathy become common and impair work and school performance, grooming, and hygiene.
Schizophrenia often has a prodromal period during which individuals become socially awkward and isolative. Negative symptoms emerge, and work or school performance gradually declines. Positive symptoms and bizarre, disorganized behavior then manifest more overtly. For example, people with schizophrenia frequently speak and laugh when they are by themselves, symptoms that are thought to represent patients’ responses to internal stimuli such as hallucinations. The negative symptoms often result in a lowered socioeconomic status, leading to unemployment, estrangement from family members, and even homelessness.
Schizophrenia is not the only cause of hallucinations and delusions. For this reason, patients presenting with psychotic symptoms need to be fully evaluated and all other potential causes of these ruled out before a diagnosis of schizophrenia is made. The presence of prominent mood symptoms during the psychotic episode indicates the likelihood of a mood disorder or schizoaffective disorder. The presence of hallucinations or delusions with subacute onset of fluctuating disturbance of consciousness and attention suggests a delirium. In the elderly, psychosis often occurs in the setting of dementia; the presence of memory loss and either aphasia, apraxia, agnosia, or loss of executive function should raise the possibility of dementia, since individuals with schizophrenia generally remain oriented to their surroundings. Hallucinations and delusions can also be induced by exogenous substances (e.g., medications, illicit drugs, and toxins) or general medical conditions such as seizure disorder, brain tumor, and encephalitis.
Abnormal psychomotor activities such as rocking, pacing, immobility, or repetitive stereotyped behaviors can impair social functioning. Hallucinations can impair concentration owing to the distraction produced by aberrant experiences. Demoralization and anhedonia, a loss of interest and enjoyment in activities, may also be found. Mortality is increased in schizophrenia; 28% of the increase in early death is attributed to suicide and 12% to accidents. The prognosis is worse in patients with impaired insight into their illness.
The lifetime prevalence of schizophrenia is 1%. Although schizophrenia occurs with equal frequency in men and women, the age of onset is earlier in males, with a peak age of onset between 10 and 25 years. Women have a bimodal age distribution with a first peak between 25 and 35 years and another peak in late middle age. The disease tends to have a more severe course in males with greater predominance of negative symptoms, and females tend to retain their social and premorbid function. However, patients with early-onset schizophrenia who live into late life usually have a many-year history of illness with prominent negative symptoms and an inability to live independently.
EARLY ONSET | LATE ONSET | |
|---|---|---|
Age of onset | Teens–early adult | Fifth decade or later |
Family history of schizophrenia | Frequently a positive family psychiatric history | Rare |
Gender | Equal prevalence between men and women | Predominantly women |
Symptom type | Negative and positive | Mostly positive symptoms; thought disorder rare |
Prognosis | Poor | Moderate |
A consensus of international experts has identified two diagnostic forms of late age disease: late-onset schizophrenia, with onset after the age of 40 years, and very-late-onset-schizophrenia-like psychosis, with onset after the age of 60 years.
Schizophrenia beginning after the age of 40 years is characterized by prominent positive symptoms, but fewer negative symptoms than early-onset schizophrenia. However, thought disorder is rare in the late-onset condition. In addition, individuals with late-onset schizophrenia are less likely to have a family history of schizophrenia than those with early onset and are more likely to be female. Compared to the cognitive deficits seen in early-onset patients, late-onset illness is characterized by relatively intact learning, abstraction, and cognitive flexibility. Very-late-onset schizophrenia frequently occurs in the setting of sensory impairment (decreased auditory acuity and low vision states) and social isolation. It is important to note that late-onset schizophrenia is responsive to lower levels of antipsychotics than early-onset schizophrenia.
Differential Diagnoses
Mood disorders include both major depressive disorder and bipolar affective disorder. In both, depressive episodes characterized by a loss of vital sense (a sense of physical discomfort, sleep disorder, appetite loss, poor self-attitude (lack of self-confidence, self-blame, and guilt), and sad mood. Bipolar affective disorder differs from major depressive disorder in that those affected also experience manic episodes. Although psychosis is not required for diagnosis, it can occur during either severe depressive or manic episodes.
One important distinction between psychosis in mood disorders and schizophrenia is that in the psychosis of mood disorders, symptoms are present only during severe mood episodes and resolve when the mood disturbance resolves. Although those with schizophrenia may experience mood symptoms during the course of their illness, psychosis is the dominant feature that persists regardless of mood disturbance. Another clinically useful distinction is that the delusions of mood disorder are congruent with the patient’s mood state. For example, in mania, grandiose delusions accompany euphoric or elevated mood, while, in depression, self-blaming, self-deprecating, and guilty delusions parallel a sad mood.
