Lamotrigine for Treatment-Resistant Seasonal Affective Disorder
Lamotrigine augmentation can be considered as a reasonable treatment option for patients with seasonal affective disorder who have failed first-line therapies (light therapy and SSRIs), particularly when there are features suggesting bipolar spectrum illness. 1
Evidence Base and Clinical Context
The evidence supporting lamotrigine in SAD is limited but promising:
A retrospective study of 30 SAD patients showed statistically significant improvement in HAM-D scores at 4 and 8 weeks (but not at 2 weeks) when lamotrigine was added to antidepressant medications. 1 This suggests lamotrigine augmentation requires patience, with meaningful response emerging after one month of treatment.
Lamotrigine is FDA-approved for maintenance therapy in bipolar disorder in adults, which is relevant because SAD is frequently associated with bipolar disorder II. 2 This approval provides a regulatory foundation for its use in mood disorders with seasonal patterns.
When to Consider Lamotrigine
Use lamotrigine augmentation specifically when:
- The patient has failed an adequate trial of light therapy (2,500-10,000 lux for 30-60 minutes daily) 3
- At least one SSRI trial at therapeutic doses for 8+ weeks has been ineffective 3, 4
- There are any features suggesting bipolar spectrum illness (history of hypomania, family history of bipolar disorder, or antidepressant-induced mood destabilization) 4
Treatment Algorithm
Start lamotrigine as augmentation to the existing antidepressant rather than monotherapy:
- Continue the current antidepressant (preferably sertraline or fluoxetine, which have the strongest evidence in SAD) 4, 5
- Add lamotrigine using standard titration protocols to minimize risk of serious rash
- Expect therapeutic response at 4-8 weeks, not earlier 1
- Monitor for serotonin syndrome when combining serotonergic agents 6, 7
Important Caveats
The evidence for lamotrigine in SAD is substantially weaker than for first-line treatments:
- Light therapy has response rates of approximately 80% in selected populations 5
- SSRIs (sertraline, fluoxetine) have demonstrated efficacy in randomized controlled trials 4, 5
- Bupropion XL has the strongest evidence for preventive treatment, reducing recurrence rates in large placebo-controlled studies 8
Before using lamotrigine, ensure the patient has truly failed first-line therapies:
- Light therapy must be administered correctly (adequate intensity, duration, and timing—morning is superior to evening) 2, 5
- SSRI doses should be at standard antidepressant levels (not the higher doses required for OCD) 6, 7
- Treatment duration must be adequate (at least 8 weeks at therapeutic doses) 3
Alternative Strategies if Lamotrigine is Not Appropriate
If lamotrigine augmentation is declined or contraindicated:
- Switch to bupropion XL, which has superior evidence for both acute and preventive treatment 3, 8
- Consider cognitive behavioral therapy, which has demonstrated effectiveness in SAD 3, 5
- Ensure light therapy is optimized before abandoning it (many patients use inadequate devices or incorrect timing) 2, 5