Says a new study, anxiety may modify depression for better or for worse, thereby, establishing a link between anxiety and depression, claiming that they co-occur.
The study, in the journal Cognitive, Affective and 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.
In their research, boffins used functional Magnetic Resonance Imaging (fMRI) at the Beckman Institute's Biomedical Imaging Center to look at brain activity in subjects who were depressed and 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," said University of Illinois psychology professor Gregory A. Miller, who led the research with Illinois psychology professor Wendy Heller. "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."
In the 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, anxious arousal (vigilance, fear, panic) enhanced activity in that part of the right frontal lobe that is also active in depression, but only when a person's level of anxious apprehension, or worry, was low. Neural activity in a region of the left frontal lobe, an area known to be involved in speech production, was higher in the depressed and worried-but-not-fearful subjects.
Despite their depression, the worriers also did better on the emotional word task than those depressives who were fearful or vigilant. The worriers were better able to ignore the meaning of negative words and focus on the task, which was to identify the color - not the emotional content - of the words.