Uncovering Meaningful Patterns in Schizophrenia: A Longitudinal Study of 9 Symptoms
Symptom research in schizophrenia focused on the reduction of the heterogeneity common to the illness presentation, course, and outcome has typically emphasized the goal of identifying meaningful schizophrenic subtypes. Current interest in the existence of multiple illness domains, occurring in various combinations across the illness course, highlight the need for exploration of the temporal patterns of symptoms common to the Positive, Disorganized, and Negative symptom groups and the interaction between symptoms, domains and key variables.
The study’s broad objective was to examine the 3-year longitudinal course of nine symptoms of schizophrenia in order to (1) model and the describe the symptom patterns (2) determine if subjects differ in symptom severity, rates and direction of symptom change (3) verify if systematic differences in the symptom patterns were attributable to medication, gender, race, diagnosis, illness phase or type of psychosocial intervention.
Subjects were 171 individuals diagnosed with schizophrenia spectrum disorders followed prospectively for 36 months in 3 distinct models of community-based care as part of an NIMH funded study. Analyses of symptom data collected every 6 months from the Brief Psychiatric Rating Scale, Community Adjustment Form and Quality of Life Scale was conducted using growth curve modeling (HLM) and longitudinal factor analysis (P-technique) to estimate symptom trajectories and examine individual subject variation and the interrelationships between the trajectories and covariates.
Results provide empirical evidence of complex, nonlinear symptom patterns with variation in individual subject intercepts, slopes, and rates and direction of change. Differences in symptom patterns were distinguished by each client and treatment variable; higher symptom severity was observed for individuals with longer illness length and more stable, less severe symptomatology characterized individuals receiving higher intensity services. Positive symptom (hallucinations and delusions) trajectories were impacted by medication use. The longitudinal factor analysis showed that both a 2-factor Positive/Negative and a 3-factor model that specified a Positive and two Negative factors, fit the data; these findings suggest that the Positive/Negative symptom dimensions have distinct longitudinal trajectories, that there is dimensionality in the Negative Factor (separating blunted affect and alogia from avolition and anhedonia) and longitudinally, the Disorganized symptoms (formal thought disorder, bizarre behavior, and attentional impairment) may not constitute a separate factor.
Future application of longitudinal methodologies designed to incorporate individual symptom variation is necessary to develop more specific and effective psychosocial interventions. Empirical confirmation of wide heterogeneity in symptomatology supports the need for individualized assessment based specifically on the presence of symptoms, the severity of symptoms, and the range and amount of fluctuations in symptom levels during any given time period—each which may have a significant impact on an individual’s overall life satisfaction, ability to participate fully in psychosocial interventions, and to maximize the capacity to function in work, social and independent living.