Interventions
Without physiologic assessments, understanding the patient’s “natural” sleep schedule can allow for rational recommendations about using phototherapy and oral melatonin (Figure21). However, referral to a sleep specialist is required unless the general psychiatrist has experience in treating circadian rhythm sleep disorders.
Morning phototherapy. Properly timed morning bright light therapy (≥2,500 lux) has been shown to help DSPD patients achieve physiologically measured sleep phase advances, objective improvements in daytime alertness, and earlier reported bedtimes compared with controls.22 Unfortunately, the described 2-hour treatment duration make this research protocol clinically impractical, and most clinicians commence with a 30-minute duration of therapy, as described in the seasonal affective disorder literature.
Relatively new and widely available blue light boxes have been reported to exhibit at least equivalent efficacy to bright light devices (as reported in the literature pertaining to seasonal affective disorder), but with markedly decreased light intensity and fewer associated adverse effects.23 As the research addressing their use in the treatment of circadian rhythm sleep disorders is still emerging, their future role remains uncertain.
Precautions. Most psychiatrists would not perform a physiologic determination of a patient’s circadian phase, and further undesired phase delays can occur if phototherapy is administered before the core body temperature minimum (Tmin).24 Also, use caution if prescribing phototherapy to patients taking photosensitizing drugs and/or those with ocular or retinal pathology.20
Evening light avoidance. Whether or not you prescribe morning phototherapy, recommending that DSPD patients avoid evening light is essential to avoid further induction or exacerbation of phase delays. Protective eyewear is warranted in instances where these advisory precautions are insufficient (see Related Resources). Such an intervention has been shown effective in decreasing light exposure and undesired phase advances in studies involving subjects exposed to simulated shift work.25
Oral melatonin. Abundant evidence supports melatonin use in achieving phase advances in individuals with DSPD.26,27 A synergistic effect can be obtained when melatonin is combined with phototherapy.28
Proper timing of melatonin to achieve a maximal phase advance can be estimated based on the individual’s dim light melatonin onset (DLMO), which occurs approximately 14 hours after the habitual (unrestricted) wake time.29 Maximal phase advances appear to occur when melatonin is given approximately 6 hours before the DLMO.26 Thus, a rational practice is to recommend that patients take melatonin 8 hours after their natural wake time. Doses of ≤0.5 mg appear to achieve the maximal chronobiotic effect while avoiding an undesired hypnotic effect.30
Precautions. Verifying the purity of over-the-counter melatonin is difficult. A review by the National Academy of Sciences states that short-term use of melatonin, ≤10 mg/d, appears to be safe in healthy adults but recommends caution in children/adolescents and women of reproductive age. Doses recommended for circadian-based interventions are typically physiologic in nature (i.e., ≤0.5 mg), which may serve to mitigate these concerns.
Adverse effects such as headaches, somnolence, hypotension, hypertension, gastrointestinal upset, and exacerbation of alopecia areata have been reported at higher melatonin doses in healthy adults and at lower doses in persons with preexisting central nervous system, cardiovascular, gastrointestinal, or dermatologic conditions.31
Figure Light and melatonin phase response curves: Normal vs. delayed
This schematic compares ‘normal sleep’ phase response curves (PRCs) to light and exogenous melatonin with postulated PRCs for an individual with delayed sleep phase disorder (DSPD), presumed to be 5 hours ‘out of phase.’ Y-axis shows the direction and relative magnitude of phase shifts produced by light or melatonin at times shown on the x-axis. X-axis covers >24 hours to better illustrate the PRCs.
Relationships between ‘normal sleepers’ and DSPD patients are depicted by:
- rectangles (sleep period)
- triangles (core body temperature minimum [Tmin])
- arrows (dim light melatonin onsets [DLMOs]).
‘Normal’ sleep is shown to occur from midnight to 8 AM, and the DSPD patient’s sleep from 5 AM to 1 PM; DLMO and Tmin are similarly delayed by 5 hours in the DSPD patient. This schematic assumes that phase relationships are maintained in DSPD patients, which is not a certainty.
Source: Adapted from reference 21
CASE CONTINUED: Under the bright lights
Jason starts phototherapy treatment during his winter break, administering bright light daily upon natural awakening using a 10,000 lux light box for at least 30 minutes. As instructed, he gradually advances the time of administration by approximately 30 minutes every other day, striving for a nocturnal sleep period of 11 PM to 7 AM. He also wears protective eyewear to reduce light exposure during evening hours to avoid further delays in sleep phase. To further promote a phase advance, he takes oral melatonin, 0.5 mg/d at approximately 8 PM, as determined by his self-report and results of actigraphic recording.