New research based on four decades of longitudinal data indicates that it is rare for a person to receive and keep a single mental disorder diagnosis. Rather, experiencing different successive mental disorders appears to be the norm.
The findings, published in JAMA Open, suggest that psychiatrists and other mental health professionals should move toward adopting a life-course perspective on mental disorders.
“The practice of diagnosing mental disorders is at a crossroads. The Diagnostic and Statistical Manual of Mental Disorders (DSM), which provides guidelines for diagnostic practice, is being questioned, not just by the ‘anti-psychiatry’ movement, but by detractors within the discipline itself,” explained study author Avshalom Caspi, a professor of psychology and neuroscience at Duke University.
“The U.S. National Institute of Mental Health, a major funder of mental health research internationally, has called for a new approach to studying mental illness, to be shaped by investigating research domains rather than by investigating traditional categorical diagnoses. And the public is confused about what constitutes a mental disorder, a confusion resulting in ‘diagnosis shopping.'”
“Our thesis is that progress in conceptualizing mental disorders has been delayed by the field’s limiting focus on cross-sectional information. Mental-health professionals typically encounter a patient at one point in his or her life. This cross-sectional view fosters a focus on the current presenting disorder, on the assumption that diagnosis informs about etiology and prognosis. But we actually know very little about how mental disorders unfold over the life span,” Caspi said.
The researchers examined data from the Dunedin Longitudinal Study in New Zealand, which used repeated standardized psychiatric assessments to track 17 mental health conditions from age 11 to age 45. The study included more than one thousand participants and the mental health conditions were diagnosed according to DSM criteria.
“These disorders included externalizing disorders (for example, ADHD, conduct disorder, substance dependence), internalizing disorders (for example, depression, anxiety, eating disorders, PTSD), and thought disorders (for example, mania, schizophrenia, OCD). This is the most detailed time series of mental-disorder life-histories ever assembled,” Caspi explained.
The study also included neurocognitive examinations during childhood and adolescence, along with a neuroimaging-based assessment of brain aging at age 45.
About one-third of the participants experienced the initial onset of a disorder by age 15 years and 86% met the criteria for at least one disorder by age 45 years.
The researchers found an “ebb and flow” of mental disorders over time. Participants with a disorder from any one of the three diagnostic families were at higher risk for disorders from other diagnostic families in the future. Participants characterized by one consistent mental disorder were not the norm.
“The primary finding is that over decades, individuals experience many changing disorder types, shifting between internalizing, externalizing, and/or thought disorder families. People seldom ‘get’ one disorder and keep it. Every disorder predicted significantly increased risk for every other disorder,” Caspi told PsyPost.
Another study based on register data from 5.9 million people living in Denmark from 2000 to 2016 has found similar results. “Our findings are buttressed by a companion study of decades of the Danish psychiatric register, which also found that most patients shift diagnoses, and every disorder predicts increased risk for every other disorder,” Caspi explained.
“These results account for findings that are now emerging from genetics and in neuroscience: Different psychiatric disorders share the same etiological factors in the genome and brain. It should not be surprising that different psychiatric conditions have the same causes, because our research shows that the same person, if tracked over years, has multiple different psychiatric conditions.”
The researchers also found several factors that influenced vulnerability to psychopathology.
“Better than any particular diagnosis, three parameters described each person’s mental health over their life: (a) age of onset, (b) duration of symptom history, and (c) number of different kinds of comorbid disorder symptoms. People with younger onset of symptoms, more years with symptoms, and more different kinds of symptoms tended to be the same people. These people also had more indicators of poor brain health at age 3, steeper child-to-adult cognitive decline, and older brain-age on structural MRI at midlife,” Caspi explained.
“This finding cautions against over-reliance on etiological theories, research hypotheses, and clinical protocols that are specific to one diagnosis. Studying disorders one at a time does not accurately represent most patients’ lived experience of shifting across disorder families.”
“Studying one disorder may mislead about specificity and hide transdiagnostic discoveries from view. There is a need for measurement instruments that capture shared liability to shifting disorders across the life course in order to make discoveries more efficiently. There is also a need to develop transdiagnostic treatments that can prevent many different conditions,” Caspi said.
The study, “Longitudinal Assessment of Mental Health Disorders and Comorbidities Across 4 Decades Among Participants in the Dunedin Birth Cohort Study“, was authored by Avshalom Caspi, Renate M. Houts, Antony Ambler, Andrea Danese, Maxwell L. Elliott, Ahmad Hariri, HonaLee Harrington, Sean Hogan, Richie Poulton, Sandhya Ramrakha, Line J. Hartmann Rasmussen, Aaron Reuben, Leah Richmond-Rakerd, Karen Sugden, JasminWertz, Benjamin S. Williams, and Terrie E. Moffitt.
