Dear Editor,
Patients with major depressive disorder (MDD) commonly experience residual symptoms even after achieving clinical remission. Sleep disturbances are among the most prevalent and clinically impactful of these residual symptoms. They can occur prior to the onset of a depressive episode, persist throughout the acute phase of the disorder, and endure long after remission has been achieved.
The STAR*D study demonstrated the high prevalence of residual sleep disturbances in this group (1). In patients who responded to treatment but did not achieve remission, the most frequent persistent sleep problem was difficulty staying asleep (middle insomnia), observed in 81.6% of patients, followed by difficulty falling asleep and early morning awakenings, which were reported by 57.5% and 49.0% of patients, respectively. Even among remitted patients, middle insomnia remained the most common residual symptom.
The existing literature demonstrates that the clinical significance of insomnia as a residual symptom is not limited to sleep complaints alone, but is also associated with impaired psychosocial functioning, decreased quality of life, and an increased risk of recurrence (2). Furthermore, insomnia is also a predictor of future depressive episodes.
The evaluation of residual insomnia can present challenges in routine clinical practice. Because clinicians tend to prioritize the improvement of mood symptoms, ongoing sleep issues can sometimes be missed or inadequately addressed during clinical assessments. In addition, certain antidepressants can alter sleep architecture or cause sleep-related adverse effects, complicating the distinction between residual symptoms and treatment-related side effects (3).
Research indicates that both pharmacological and non-pharmacological treatments can be effective in reducing residual insomnia symptoms in MDD. Cognitive behavioral therapy, mindfulness-based practices, structured exercise programs, and appropriate pharmacotherapy for insomnia represent promising approaches to improving sleep-related outcomes in patients with residual depressive symptoms (4, 5).
Consequently, residual insomnia remains a highly prevalent and clinically significant symptom following recovery. Regular assessment of sleep disorders can assist in identifying patients who are at heightened risk of functional impairment and relapse. Therefore, increased clinical attention to residual insomnia may contribute to a more holistic and lasting recovery in patients with MDD.
