Work functioning appears to be related to the course of the illness, verbal learning and recent depression, while the mental ability to process information quickly is associated with overall as well as social functioning.
“Processing speed is robustly associated with social and global functioning in bipolar disorder. Poor work functioning is significantly related to subsyndromal depression, course of illness, and verbal learning deficits,” according to Dr. Joseph Goldberg of the Mount Sinai School of Medicine, and his research team.
Bipolar disorder, also known by its older name, “manic depression,” is a mental disorder that is characterized by alternating moods. A person with bipolar disorder experiences “highs” (what clinicians call “mania“) and “lows” (depression). Bipolar disorder affects approximately 5.7 million American adults, according to the National Institute of Mental Health, and is the sixth leading cause of disability worldwide, according to the WHO. A number of studies in recent years have confirmed the presence of cognitive dysfunction in bipolar patients, not just during manic or depressive episodes, but also during periods of stability.
To evaluate how cognitive problems affect overall function relative to mood symptoms, Goldberg and his team evaluated 33 type I individuals. The participants were enrolled in the study at their first hospitalization, and followed up after 15 years.
Extensive testing of verbal learning, memory, processing speed, verbal fluency, executive function, and general knowledge was done at the beginning of the study and after 15 years. At the completion of the study, mood symptoms, cognition, work, social, and overall functioning were reassessed.
Processing speed, one measure of cognitive function, was measured using the Wechsler Adult Intelligence Scale (WAIS)-Digit Symbol test. Processing speed relates to how quickly an individual is able to visually perceive information and mentally process it.
Goldberg found that in the individuals with bipolar disorder, overall functional difficulties in life were related to decreased processing speed. Slower processing speed and decreased social functioning were also related. “Digit symbol performance also was the sole significant predictor of social functioning,” writes the team.
In addition, disability at work was associated with problems in verbal learning, the number of hospitalizations, and recent depression.
However, the researchers found that in the participants, neither their overall severity of mood symptoms nor the course of their illness was related to their overall function or social function.
“The present findings highlight the fundamental nature of cognitive impairment as a separable dimension from residual or persistent depressive features in a substantial number of individuals with bipolar disorder at follow-up, and point to the need for assessing cognitive status as well as affective symptoms in future studies of functional outcome,” writes Goldberg and his colleagues. “Cognitive and mood symptoms warrant consideration as independent determinants of functioning in patients with bipolar disorder many years after an index manic episode.”
The relationship between cognitive dysfunction and bipolar disorder is complex. Some have hypothesized that the problems with cognition are a result of repeated mood episodes, treatment, medication, or other factors stemming from the illness. Others theorize that the same genetic, neurochemical and brain changes give rise to both issues. While this study cannot directly answer these questions, the results may give researchers additional insight. In addition, this study may help to develop better interventions to improve functional outcomes for patients with bipolar disorder.
Goldberg’s results can be found in the July issue of the journal Acta Psychiatrica Scandinavica.
Source: Acta Psychiatrica Scandinavica