Researchers at the Rhode Island Hospital have found that most psychiatric patients have more than one diagnosis.
In the study, the researchers found that the majority of 2,300 psychiatry outpatients had more than one disorder when seeking treatment, and more than one-third had at least three disorders.
The research team, led by Mark Zimmerman, M.D., director of outpatient psychiatry at Rhode Island Hospital and associate professor of psychiatry and human behaviour at Brown Medical School, used standardized interviews to evaluate a wide range of psychiatric disorders in a general clinical outpatient practice.
The researchers found that most patients had more than one diagnosis; on average, patients had 1.9 current diagnoses. Patients with principal diagnoses of post-traumatic stress disorder (PTSD) and bipolar disorder had the highest number of diagnoses.
"Based on the results of this study, clinicians should assume that in outpatients presenting for the treatment of mood or anxiety problems, the patients have more than one diagnosis," Zimmerman said.
The researchers also examined which disorders were the most common reasons for seeking treatment.
They found that major depressive disorder was most common, present in nearly half of the patients, and was usually the primary reason for seeking treatment. In contrast, social phobia was the second most common diagnosis, present in approximately 25 percent of the patients.
However, 95 percent of the patients diagnosed with social phobia came for treatment of another disorder.
"For disorders like social phobia that are infrequently diagnosed as the principle disorder in clinical practice, it will be important for the next generation of treatment-efficacy studies to determine if treatment is effective when the disorder is a comorbid condition," Zimmerman said.
The study is published in the February 2008 edition of the journal Psychological Medicine.