LINDSLEY G, CRAWFORD B Sleep Research 1996; 25: 279. Lesley College and Quintiles/Benefit Research
According to recent studies, the comorbidity rate of narcolepsy and depression is estimated to be between 30-52%, as compared with a depression prevalence rate of 8.1% in the general population. Our current study provides further support of the significantly elevated comorbidity rate of narcolepsy and depression, and extends these findings. Subjects were 22 men and 44 women between the ages of 17 and 76 (mean=49ñ15.24) who completed a survey intended to assess the financial burden of narcolepsy. Estimated age of narcolepsy symptom onset was 20 yoñ10.64. The mean age of diagnosis was 34 yo ñ 11.49 years, with a mean lag of 14ñ11.53 years from estimated year of onset. According to the subjects' retrospective reports, 46% carried an accurate diagnosis of depression prior to their diagnosis of narcolepsy. Strikingly, 56% of the sample continued to carry this diagnosis during this past year. There was also a high comorbidity with diagnoses of anxiety. 32% carried this diagnosis prior to identification of narcolepsy, which increased to a rate of 35% within the past year. Overall rate of moderate to severe mood disturbance was 58% of the sample pre-narcolepsy diagnosis, which stayed essentially the same, 57%, during the past year.
Looked at separately, the five subjects in the sample < 25 yo had a lag of 0-5 years from onset to diagnosis. The data showed essentially the same trends with respect to associated diagnoses of depression and severity of mood disturbance, except that anxiety frequency increased rather then remained the same during the past year.
With respect to co-relationships among potentially relevant variables, severity of depression was independent of reported severity of EDS, cataplexy, disruption of school or work life, and medication. As graphed below for the current year data, however, there was a striking relationship between severity of depressed mood and presence/absence of anxiety diagnoses, with anxiety diagnoses increasing as depressed mood increased. Severity of depression also had a similar relationship with difficulty focusing and concentrating (cognitive disturbance).
In conclusion: (1) The probability of depression in association with narcolepsy is very high; (2) Formal diagnoses of depression are significantly related to diagnoses of anxiety; (3) Severity of depressed mood appears also to be related to degree of cognitive disturbance; (4) Depression increased rather than decreased across the life span in these subjects whereas anxiety increased in our small sample of young people but decreased moderately from prediagnosis to the current year in the total sample; and (5) that there was no obvious relationship between subjectively reported severity of depressed mood and severity of EDS or cataplexy, degree of disruption of school or work life, or type of medication. These data reinforce how critical it is to address affective disturbance as well as the primary symptoms of narcolepsy when treating narcoleptic patients. In addition, the high comorbidity rate of depression with narcolepsy, even when EDS and cataplexy are more or less under control, raise the question of whether depression is actually a constituent rather than merely a concomitant of narcolepsy.
Research supported in part by Cephalon, Inc.
Interesting? When research is supported by drug companies, I usually am a bit skeptical, but this study isn't surprising to me, nor does it seem unlikely. What do you think about it? Leave a comment if you like, I would love to hear your thoughts on this.
Until next time,
Via Con Dios,