To complement these analyses, we compared the rates of comorbid psychiatric disorders between individuals with single-episode and recurrent depression, using data from the Danish Psychiatric Central Research Register, and found highly significant increase in comorbidity among those with recurrent depression (Extended Data Table 1). This is consistent with well-established correlations between depression symptom severity, recurrence, chronicity and comorbidities75,76. The most compelling differences were observed for anxiety (OR=1.64, P=2 x 10−53), bipolar disorder (OR=1.86, P=3.1 x 10−27), schizophrenia (OR=1.76, P=9.6 x 10−48) and SUD (OR=1.64, P=3.7 x 10−32).
