Study objective: To determine patterns and relative intensity of psychopathology, as measured by the Minnesota Multiphasic Personality Inventory (MMPI), in 108 patients with either psychophysiological insomnia (PI; n=20), insomnia with psychiatric disorder (IPD; n=30), periodic limb movement disorder (PLM; n=28), or obstructive sleep apnea (OSA; n=30).
Design: Cross-sectional.
Setting: University sleep disorders center.
Measurements and results: Subjects completed the MMPI prior to overnight diagnostic polysomnographic assessment followed by Multiple Sleep Latency Test (MSLT). Seventy five percent of the entire sample had at least one MMPI elevation (T>70). Groups showed significant baseline differences in age, BMI, and MSLT latency (all ps<.05). Logistic regression indicated that even after statistically controlling for these three diagnostic covariates, MMPI elevation was more likely among PLM and IPD patients than OSA or PI patients (all ps<.05). Followup pairwise comparisons indicated that this same pattern of group differences occurred for the Depression, Psychasthenia, and Schizophrenia scales (all ps<.05).
Conclusions: Irrespective of age, obesity, and daytime sleepiness, patients with untreated PLM or IPD are more likely to experience clinically significant psychological difficulties than those with either OSA or PI. These differences are most likely to be manifested in terms of depressive symptoms, anxiety symptoms (tension, worry, guilt), social alienation, and diminished mental concentration. Finally, PLM may be associated with greater MMPI elevations than previously suspected, and agree with earlier clinical reports of high rates of psychiatric treatment in PLM.