CHAMPAIGN, Ill. - A new study of brain activity in depressed and anxious people indicates that patterns of brain activity in depression are modified - for better or for worse - by anxiety.
The study, in the journal Cognitive, Affective & Behavioral Neuroscience, looked at depression and two types of anxiety: anxious arousal, the fearful vigilance that sometimes turns into panic; and anxious apprehension, better known as worry. Illinois doctoral alumna Anna S. Engels and Illinois psychology professors Wendy Heller and Gregory A. Miller led the research, which was based on Engels' dissertation.
The researchers used functional Magnetic Resonance Imaging (fMRI) at the Beckman Institute's Biomedical Imaging Center to look at brain activity in subjects who were depressed an not anxious, anxious but not depressed, or who exhibited varying degrees of depression and one or both types of anxiety.
"Although we think of depression and anxiety as separate things, they often co-occur," Miller said. "In a national study of the prevalence of psychiatric disorders, three-quarters of those diagnosed with major depression had at least one other diagnosis. In many cases, those with depression also had anxiety, and vice versa."
Previous studies have generally focused on people who were depressed or anxious, Miller said. Or they looked at both depression and anxiety, but lumped all types of anxiety together.
Miller and Heller have long argued that the anxiety of chronic worriers is distinct from the panic or fearful vigilance that characterizes anxious arousal.
In the new study, brain scans were done while participants performed a task that involved naming the colors of words that had negative, positive, or neutral meanings. This allowed the researchers to observe which brain regions were activated in response to emotional words.
The researchers found that the fMRI signature of the brain of a worried and depressed person doing the emotional word task was very different from that of a vigilant or panicky depressed person.
"The combination of depression and anxiety, and which type of anxiety, give you different brain results," Miller said.
Perhaps most surprisingly, an overall pattern of rightward bias (greater right- than left- hemisphere activity) was found for depression for areas of the prefrontal cortex, but only when accompanied by high anxious arousal (vigilance, fear, panic) and low anxious apprehension (worry). The type and combination of anxiety modulated the pattern of brain activation observed for depression.
In an earlier fMRI study based on Engels' masters thesis, the researchers found that the two types of anxiety produced very different patterns of activity in the brain during this type of task. People with anxious arousal lit up a region of the right inferior temporal lobe (just behind the ear). Worriers, on the other hand, activated a region in the left frontal lobe that is linked to speech production.
(Other research has found that depression, by itself, activates a region in the right frontal lobe.)
Because in the present study the overall rightward bias pattern for depression was found only when anxious apprehension was low, higher levels of worry may obscure this pattern. That is, the tendency to activate the region in the left inferior frontal lobe, as shown for worriers in the earlier fMRI study, may obscure or counteract rightward biases in brain activity for depression when depression co-occurs with anxious apprehension.
"It could be that having a particular type of anxiety will help processing in one part of the brain while at the same time hurting processing in another part of the brain," Miller said. "Sometimes worry is a good thing to do. Maybe it will get you to plan better. Maybe it will help you to focus better. There could be an up-side to these things."
Collaborators on the study include Jeffery M. Spielberg, Stacie L. Warren and Bradley P. Sutton, from the University of Illinois; and Marie T. Banich, from the University of Colorado. The National Institute of Mental Health and the National Institute of Drug Abuse at the National Institutes of Health and the Beckman Institute and Intercampus Research Initiative in Biotechnology at the U. of I. supported the research.
Miller also is affiliated with the department of psychiatry, and he and Heller are affiliated with the Beckman Institute and the Neuroscience Program at Illinois. Engels now is the assistant director of the Social, Life & Engineering Sciences Imaging Center (SLEIC) at Pennsylvania State University.