Do Word-Processing Problems Cause Social Anxiety?

There are a lot of people who are afraid of interacting with other people. In fact, social anxiety is one of the most common of all psychiatric disorders and a major public health problem.

But what is it that prompts socially anxious humans to keep their distance from others? One possible explanation is that these people have difficulty in hearing words and syllables. This hypothesis was bolstered by a study conducted by Gerard Bruder, Ph.D., a professor of clinical psychology at Columbia University, and his colleagues and reported in the January American Journal of Psychiatry.

The study included 25 subjects with social phobia; 82 subjects with a major depressive disorder, dysthmic disorder, or both; 18 subjects with social phobia plus a depressive disorder; and 44 healthy comparison subjects. All were right-handed. All were given three tests.

In the first test, they heard one word in one ear and one word in another ear at the same time. The word pair sounded very much alike, for example, “coat” and “goat.” They were then asked to report what they had heard. This way, the researchers could determine which ear heard better. The test was then repeated with other word pairs.

In the second test, they heard one syllable in one ear and one syllable in the other ear at the same time—the syllable pair also sounded very much alike, for example, “ba” and “da.” They were then asked to report what they had heard.

In the third test, they heard one tone in one ear and another tone in the other ear at the same time and then were asked to identify the pitches of the tones. This allowed the researchers to determine which ear heard better. The test was repeated with various tone pairs.

The number of each subjects’ correct responses on the right- and left-ear presentations on each test determined whether the left ear had an advantage over the right. Findings for the four groups of subjects were then compared.

All four groups were found to perform comparatively on the tone tests and whether the tones were presented to the left or right ear. All four groups were found to hear words and syllables somewhat better with their right ears than with their left ears. However, subjects with social phobia and those with social phobia plus depression demonstrated significantly less right-ear advantage in hearing words and syllables than did those subjects who were healthy or were depressed but who did not have social phobia.

These results thus suggest that socially anxious persons have difficulty hearing words and syllables with their right ears, and since hearing with the right ear is controlled by the left hemisphere of the brain, their difficulty in hearing words and syllables with their right ears may originate in the left hemisphere of their brains.

But where in the left hemisphere might things be going awry? Very possibly in the temporoparietal regions, since those areas, research suggests, mediate phonetic processing of words and syllables and since some people with anxiety disorders have less-than-normal blood flow in these regions.

Yet just because persons with social phobia may have something amiss with their left-hemispheric processing of spoken speech, that is no proof, of course, that the problem is what makes them shy. In fact, as Bruder stressed in an interview with Psychiatric News, “One cannot draw cause-and-effect conclusions from studies such as this. . . .”

In other words, the speech problem could be the cause of the social phobia, or vice versa.

In any event, “insufficient attention has been paid toward elucidating the neurobiological basis of social anxiety,” Dennis Charney, M.D., head of the National Institute of Mental Health’s Mood and Anxiety Disorders Research Program, wrote in an accompanying editorial. “In this context, the paper by Bruder and colleagues. . .is welcome. . . . Their speculation that the deficit in the left-hemisphere processing of verbal stimuli may have clinical relevance to the anxiety experienced in social situations. . . deserves further study.”

“I would be cautious about drawing clinical implications from this study,” Franklin Schneier, M.D., an associate professor of clinical psychiatry at Columbia University and one of the study’s authors, told Psychiatric News. “[Nonetheless] the findings do suggest that brain function in the comorbid condition of major depressive disorder plus social phobia differs from that of major depressive disorder alone. I think this should further encourage clinicians to carefully diagnose anxiety disorders that may be comorbid in patients presenting with depression. Treatments and follow-up assessments should [then] take the comorbid anxiety disorder into consideration.”

The study was funded by the National Institute of Mental Health.

The study, “Left Hemisphere Dysfunction During Verbal Dichotic Listening Tests in Patients Who Have Social Phobia With or Without Comorbid Depressive Disorder,” is posted online at http://ajp.psychiatryonline.org/cgi/content/full/161/1/72?. ▪

Am J Psychiatry 2004 161 72