1 - (OP12) Trajectories of Health Anxiety: A Longitudinal Comparison of Illness Anxiety Disorder and Somatic Symptom Disorder

In the DSM-5, individuals with severe health anxiety can receive either a diagnosis of Illness Anxiety Disorder (IAD) or Somatic Symptom Disorder (SSD) depending on their somatic symptom severity. While cross-sectional research suggests minimal differences between these disorders for people with health anxiety, there are no longitudinal studies comparing the course and trajectories of IAD and SSD over time. No past research has examined the stability of IAD over time in health anxious individuals.

This is the first longitudinal examination of DSM-5 health anxiety diagnoses over time. A sample of 118 participants (mean age=41 years, 84% female) completed an online survey and ADIS-5 diagnostic interview at baseline, 3-months, and 6-months. The survey included self-report measures of health anxiety, generalized anxiety, depression, quality of life, and health service use. The ADIS-5 assessed IAD, SSD and comorbid diagnoses. Linear mixed models examined the effects of health anxiety diagnoses on outcomes over time.

At baseline, 25 participants (21.2%) met IAD criteria. By 3-months, 52% continued to meet IAD criteria, 24% were in remission, and 24% met SSD criteria as they endorsed moderate to severe somatic symptoms. At 6-months, 41.2% met IAD criteria, 41.2% were in remission, 5.9% met SSD criteria, and 11.8% met comorbid IAD/SSD criteria. Compared to IAD, those with SSD had significantly higher somatic symptoms, greater health care utilization, and poorer physical health-related quality of life over time. No significant group-by-time interactions were observed, suggesting there were no differences in course between the two disorders.

These findings suggest that IAD is stable for half of health anxious individuals; the remainder recover or transition to SSD as their somatic symptoms become moderate to severe in intensity. SSD appears to be more severe and impairing than IAD over time. These findings await replication in larger nationally representative samples, across countries. The lack of other qualitative differences between IAD and SSD suggests that for these disorders should be reclassified into one health anxiety disorder in DSM-6.

For clinicians treating health anxious clients with CBT, these findings show that health anxious individuals commonly transition between IAD and SSD over time, and health anxious clients who meet IAD criteria are likely to exhibit less severe symptoms, better physical quality of life, and lower health care utilization than clients with SSD.