The SSRIs are characterized by selective inhibition of the presynaptic serotonin transporter, leading to enhanced activity of serotonin at postsynaptic receptors.3 A large number of serotonin receptor subtypes that regulate sleep and wakefulness as well as transitions between specific sleep stages, such as the termination of REM sleep, have been identified.
Because of the complexity of serotonin involvement in sleep-wake regulation, drugs that modulate serotonin activity can produce prominent and sometimes diverse effects on sleep. Some patients who took fluoxetine reported insomnia as an adverse effect, whereas other patients experienced daytime somnolence.11 This same pattern of diverse subjective reports on sleep and wakefulness has been reported in clinical trials with all of the drugs in this class.
While data have been reported most extensively for fluoxetine and paroxetine, class effects of SSRI therapy appear to include increased sleep onset latency and/or an increased number of awakenings and arousals, leading to an overall decrease in sleep efficiency.12,13 Virtually all of the SSRIs examined have been noted to suppress REM sleep.1 Clinically, reports of a change in the frequency, intensity, and content of dreaming can be associated with SSRIs, as well as the occurrence of these symptoms on discontinuation.
Be mindful that treatment of a patient with depression may produce significant improvement in symptoms of depression in general, yet may not address insomnia. In some cases, treatment with an SSRI may produce or exacerbate problems with sleep disturbance. Therefore, a medication that targets insomnia may also be prescribed for patients with depression who are being treated with an SSRI.