30 June 2011. A new study throws a bright light on the difficulty of diagnosing psychotic disorders. Published online June 15 in the American Journal of Psychiatry, the study found that the diagnosis initially given to 50 percent of study participants who had been admitted to the hospital for psychosis changed at least once during the ensuing 10 years. These shifts mainly reflected changing symptoms over the course of life, rather than misdiagnoses.
"Everyone knows that symptoms and illness course and life circumstances change over time. But a significant message of this paper is that these factors can alter the central diagnosis, which typically is not revisited," said Evelyn Bromet of Stony Brook University School of Medicine, who led the study. "When studying adults, everybody assumes that they've grown up and matured and they're not moving targets anymore. But it's not true."
The findings mark the most recent installment of a longitudinal study comparing diagnoses given at first admission for psychosis, six months, two years, and 10 years afterward. The four time points reveal illness trajectories that fluctuate across five broad diagnostic categories, which included schizophrenia, bipolar disorder, major depression, substance-induced psychosis, and other psychotic conditions. Most changes consisted of shifts from a non-schizophrenia category at baseline to schizophrenia later in life, with one-third of this group getting the schizophrenia diagnosis after year two.
"I think the assumption was that we sorted the diagnosis out by two-year follow-up," Bromet told SRF. "But we found a lot can change between two and 10 years."
One decade later
When the study began in the late 1980s, Bromet hadn't expected diagnoses to change much, especially after the six-month follow-up timepoint. But when contacting people later, it became clear that symptoms had often changed enough to warrant a new diagnosis. "When we started, longitudinal studies did not re-diagnose people," she said.
For the new study, diagnoses were made at 10 years for 470 people who had been systematically assessed at their first hospital admission for psychosis, six months later, and two years later. The same procedure was used to make a diagnosis at each time point: a mental health professional interviewed each person face to face, and at least four psychiatrists used these and previous assessments, medical records, and interviews with family members to settle on a diagnosis. However, the psychiatrists remained blind to previous research diagnoses.
The data revealed a major shift toward schizophrenia diagnoses. Of participants receiving a non-schizophrenia diagnosis at baseline, 32 percent eventually received a schizophrenia diagnosis at year 10. Of those initially receiving a non-bipolar disorder diagnosis, 10 percent ultimately received a bipolar diagnosis at year 10.
The detailed distribution at baseline was 30 percent schizophrenia, 21 percent bipolar disorder, 17 percent major depression, 2 percent substance-induced psychosis, and 28 percent other psychoses. At year 10, this became 50 percent, 24 percent, 11 percent, 7 percent, and 8 percent, respectively. The increase in schizophrenia and bipolar diagnoses, coupled with the decrease in the "other" category, suggests that these illnesses can take time to make themselves apparent.
Diagnostic stability on the horizon?
Does the 10-year diagnosis reflect a stabilizing illness course, or yet another fluctuation in symptoms? Consistent with the idea that diagnostic stability can eventually be achieved for some cases, baseline diagnoses of schizophrenia and bipolar disorder largely held true at year 10, with 90 percent of initial schizophrenia diagnoses and 78 percent of initial bipolar disorder diagnoses retained.
Still, 50 percent of study participants received a different diagnosis at least once during the follow-up period, and their trajectories differed: some ended up with the same initial diagnosis with which they began, whereas others received a wholly different diagnosis. To explore whether these fluctuations would dampen with time and stabilize upon one diagnosis, Bromet plans to reassess the cohort at 20 years.
The researchers also tracked down the changes in the clinical picture that spurred the diagnostic shifts. Whereas poorer functioning and greater negative and psychotic symptoms predicted a shift to schizophrenia, better functioning and lower negative and depressive symptoms predicted a shift to bipolar disorder.
If clearer diagnostic pictures emerge with time, the results are bound to concern clinicians and researchers alike. Shifting diagnoses not only complicate treatment strategies, but they also muddy the waters for genetic and postmortem research, which depends on a reliable diagnosis as a starting point.
"It's really only fair, if you're treating somebody, to reconsider the diagnosis," Bromet said. "It doesn't mean a diagnosis made 10 years ago wasn't valid then. It just means that it may or may not be valid today."—Michele Solis.
Bromet EJ, Kotov R, Fochtmann LJ, Carlson GA, Tanenberg-Karant M, Ruggero C, Chang SW. Diagnostic Shifts During the Decade Following First Admission for Psychosis. Am J Psychiatry. 2011 Jun 15. Abstract