The researchers also found that depressed patients who didn't respond to the antidepressant fluoxetine (Prozac) had lower concentrations of mu receptors in the anterior cingulate, an area of the brain involved in the processing of emotional states.
In other studies, NIMH researchers used PET and functional MRI to identify abnormal patterns of neural activity and chemical function in the brain's reward pathway that underlie depressed patients' inability to experience pleasure.
"The identification of brain systems and circuits whose activity can be correlated with specific symptoms is a first step toward the development of more targeted and effective treatments for depression and other disorders of the brain," Dr. Wayne Drevets, of the NIMH, said in a prepared statement.
In another study, Yale School of Medicine researchers using specialized applications of MRI found that people with bipolar disorder have reduced volume of the brain's prefrontal cortex and its subcortical connections sites, including the amygdala.
Previous research found that patients with bipolar disorder have abnormal functioning of these brain structures, especially during the processing of emotional stimuli and during tasks that require inhibition of impulsive responses.
In other studies, scientists found that fMRI can help determine whether children have biploar disorder or severe irritability with attention-deficit hyperactivity disorder (ADHD). This suggests that brain imaging may prove useful in making a correct diagnosis.
"We're finding that these very irritable children with ADHD share some characteristics with children with bipolar disorder but also have significant differences," said Leibenluft.
Children with these conditions are easily frustrated, have difficulty reading facial emotional cues, and have social cognition deficits.
"Yet what's happening in the brain during frustration differed between the two groups. So these data indicate that, even when two groups of patients exhibit the same symptoms, the brain mechanisms underlying that symptom can differ. Data like these indicate how, eventually, psychiatric diagnosis will be based on brain mechanisms, in addition to symptoms," Leibenluft said.
More information
The U.S. Center for Mental Health Services has more about mood disorders.
