The negative symptoms of schizophrenia have been recognized for 100 years. Characterized by a loss of a function that should be present, negative symptoms include anhedonia, asociality, amotivation, and affective blunting. Individuals with schizophrenia who have a preponderance of negative symptoms (“deficit syndrome”) may comprise a special subset of patients. Compared with positive symptoms, negative symptoms are associated with worse global functioning and worse response to antipsychotic medication. Treatment of negative symptoms is challenging. Secondary negative symptoms—those that simulate or resemble primary negative symptoms but are attributable to another cause, such as major depressive disorder or the adverse effects of antipsychotic medication—need to be ruled out. Emerging evidence suggests that newer antipsychotics with novel mechanisms might be effective in treating negative symptoms. Antidepressants might also play a role.
This article describes types of negative symptoms, their clinical relevance, neuroanatomical and neurotransmission factors associated with negative symptoms, and current and future treatment options.
Modest improvements with antipsychotics
Schizophrenia affects an estimated 1% of the population.1 Antipsychotic medication has been the mainstay of schizophrenia treatment since chlorpromazine was introduced in the 1950s; it was soon followed by many other antipsychotics. These first-generation antipsychotics (FGAs) were joined by second-generation antipsychotics (SGAs) in the 1990s. While SGAs are better tolerated and less likely to induce extrapyramidal side effects (EPS) than FGAs, they also are associated with troubling metabolic adverse effects (eg, impaired glucose tolerance).1
All antipsychotics are believed to exert their therapeutic effects by blocking dopamine (D2) receptors and are effective in ameliorating the positive symptoms of schizophrenia, including hallucinations, delusions, bizarre behavior, disordered thinking, and agitation.1 Early research had suggested that SGAs might also reduce the negative symptoms of schizophrenia, perhaps because they also block serotonin 2A receptors, a property thought to broaden their therapeutic profile. Over time, it became clear that neither FGAs nor SGAs conferred an advantage in treating negative symptoms, and that the observed improvements were modest.2-5 However, recent research suggests that several newer antipsychotics might be effective in targeting negative symptoms.2,6,7
History of negative symptoms
In the early 20th century, Swiss psychiatrist Eugen Bleuler coined the term schizophrenia to emphasize the cognitive impairment that occurs in patients with this illness, and which he conceptualized as a fragmenting of the psychic process.8 He believed that certain symptoms were fundamental to the illness, and described affective blunting, disturbance of association (ie, distorted thinking) autism (ie, impaired relationships), and ambivalence (ie, fragmented emotional responses). He viewed hallucinations and delusions as accessory symptoms because they were not unique to schizophrenia but were also found in other disorders (eg, mood disorders). Bleuler’s ideas took root, and generations of psychiatrists were taught his fundamental symptoms (“the 4 A’s”), the forerunner of today’s negative symptoms. Later, other experts chose to emphasize psychotic symptoms as most characteristic of schizophrenia, including Schneider’s “first-rank symptoms,” such as voices conversing or delusions of passivity.9
Negative symptoms were rediscovered in the 1970s and 1980s by psychiatric researchers interested in descriptive phenomenology.10,11 Research confirmed the presence of a positive dimension in schizophrenia characterized by the loss of boundaries between the patient and the real world (eg, hallucinations, delusions), and a negative dimension characterized by the loss of a function that should be present, such as alogia and asociality. These experts carefully described negative symptoms and created scales to measure them, including the Scale for the Assessment of Negative Symptoms (SANS),12 the Positive and Negative Syndrome Scale (PANSS),13 the Brief Negative Symptom Scale (BNSS),14 and the 16-item Negative Symptom Assessment (NSA-16).15 Contemporaneous to this work, a “deficit syndrome” was identified among patients with schizophrenia with prominent negative symptoms. The deficit syndrome is found in 25% to 30% of chronic cases.16 Negative symptoms are very common in patients with schizophrenia (Table 19).8,17
Early editions of the DSM defined schizophrenia mainly on the basis of disturbance of cognition, mood, and behavior, and a retreat from reality. With the publication of DSM-III in 1980, and in subsequent editions, schizophrenia was redefined as a relatively severe psychotic illness in which positive and negative symptoms were present, thereby acknowledging the importance of Bleuler’s fundamental symptoms. In DSM-5, negative symptoms are described as accounting for “a substantial portion of the morbidity associated with schizophrenia but are less prominent in other psychotic disorders.”18
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