A new study finds a flaw in the method by which mental health disorders have been tracked, leading to a miscalculation of the prevalence of mental disorders among middle-aged and older adults.
Researchers from the Johns Hopkins Bloomberg School of Public Health discovered assessment methods that relied on a person’s recall of events may lead to an underestimate of mental conditions.
Interestingly, the same recall methods provided relatively accurate measurement of past physical maladies.
Researchers believe the stigma surrounding mental illness, the intermittent course of many mental illnesses and the challenge in defining and measuring mental health issues may all contribute to the reporting variance.
The study by Yoichiro Takayanagi, M.D., Ph.D., is published in the online edition of JAMA Psychiatry.
Takayanagi uncovered substantial discrepancies among mid-life and late-life adults in reporting past mental health disorders — including depression — as compared with physical disorders such as arthritis and hypertension.
“The takeaway is that lifetime estimates based on [participant] recall in cross-sectional surveys underestimate the occurrences of mental disorders over the lifetime,” said Ramin Mojtabai, M.D., Ph.D., MPH, MA, associate professor and senior author of the study.
The findings are believed to be the first to examine retrospective evaluations versus cumulative assessments among older adults.
Recent studies of adolescent and young adults have also found discrepancies in prevalence estimates of common mental disorders between retrospective reports versus multiple assessments over time.
The study was based on interviews in 2004 and 2005 with 1,071 adults who had since the early 1980s participated in the Baltimore Epidemiologic Catchment Area Survey, a longitudinal study that included three earlier sets of interviews going back 24 years.
When asked to provide so-called retrospective evaluations in six categories — depression, obsessive-compulsive disorder, panic disorder, social phobia, alcohol/drub abuse — participants underreported their disorders even though they had reported them one or more times in three previous assessments.
In contrast, the same cohort, when asked for retrospective evaluations of physical disorders in five categories — diabetes, hypertension, arthritis, stroke, cancer — provided histories that were much closer to cumulative assessments from the earlier interviews. For instance, only one out of 10 underreported that they’d previously had diabetes.
As part of the study, trained interviewers administered a structured interview that yields psychiatric diagnoses based on DSM-III or DSM-III-R criteria, in four waves of interviews.
In the first two waves, in 1981 and again in the 1982, DSM-III was used. In the third follow-up, which took place in 1996, and the fourth, in 2004 and 2005, the DSM-III-R was used.
Failure to recall lifetime mental disorders was defined as not meeting criteria for the lifetime history of the mental disorder in the fourth round of interviews, despite reporting symptoms that met criteria for that disorder in at least one previous interview.
The study found that the lifetime estimates of mental disorders ascertained by retrospective versus cumulative evaluations were:
- 4.5 percent versus 13.1 percent for major depressive disorder;
- 0.6 percent versus 7.1 percent for obsessive-compulsive disorder;
- 2.5 percent versus 6.7 percent for panic disorder;
- 12.6 percent versus 25.3 percent for social phobia;
- 9.1 percent versus 25.9 percent for alcohol abuse or dependence, and;
- 6.7 percent versus 17.6 percent for drug abuse or dependence.
In contrast, the estimates of physical disorders measured by retrospective versus cumulative evaluations were:
- 18.2 percent versus 20.2 percent for diabetes;
- 48.4 percent versus 55.4 percent for hypertension;
- 45.8 percent versus 54.0 percent for arthritis;
- 5.5 percent versus 7.2 percent for stroke, and;
- 8.4 percent versus 10.5 percent for cancer.
Mojtabai explained that the contrast between the recall of mental and physical disorders is noteworthy and may be attributable to differences in age at onset and the course of these disorders.
“Stigma associated with mental disorders, as well as the fluctuating course of mental illnesses, might partly explain the discrepancies, as well as differences in ages of onset of mental and physical disorders.
“Mental disorders start earlier and have a higher prevalence in early to mid-life, whereas physical disorders are typically illnesses of middle and older age and tend to be chronic.”
The authors noted that measurement issues might also help explain the differences in recall of mental and physical illnesses.
Ascertainment of mental disorders was based on symptom criteria, while ascertainment of physical illnesses was based on the participant’s report of presence versus absence of a particular physical disorder.