The clinical context: differentiating cause and effect
A presentation of IH, characterised by a short mean sleep latency on MSLT, is often accompanied by symptoms that overlap with depression: sleep inertia, heavy limbs, lack of motivation, concentration difficulties and persistent fatigue. This overlap complicates the clinical picture, as it is not always possible to determine whether the depressive symptoms are primary or secondary to the profound sleepiness of IH. For some patients with IH, the mood disturbance appears to be a consequence of chronic fatigue and functional impairment.
This hypothesis is supported by case reports in the literature, where modafinil has been observed to address both the sleepiness and the associated depressive symptoms. In a case series of patients with partial response to antidepressants, the addition of modafinil resulted in improvements in wakefulness and fatigue, which were associated with substantial improvements in functioning and, in some cases, a reduction in depressive symptoms. This suggests the therapeutic effect on mood may be indirect, stemming from the restoration of daytime function.
The evidence: mood, anxiety and depression
The evidence for modafinil's direct effect on mood and anxiety is mixed and warrants careful interpretation.
Effects on mood and depression
A randomised, double-blind, crossover trial in healthy volunteers found that modafinil (400 mg daily) increased positive affect and general mood scales. However, it also significantly increased scores on the Negative Affect scale, which the authors interpreted as an increase in anxiety. This dual effect is a key clinical consideration.
A letter to the editor described a case where a patient with treatment-resistant depression experienced marked improvement in depressive symptoms on a low dose (100 mg/day) of modafinil monotherapy after failing multiple antidepressant trials. The symptoms resolved with modafinil but recurred upon discontinuation.
| Source of evidence | Reported finding |
|---|---|
| Crossover trial, healthy volunteers (400 mg/day) | Increased positive affect and general mood; also increased Negative Affect scores |
| Case report, treatment-resistant depression (100 mg/day) | Marked symptom improvement; recurrence on discontinuation |
| Systematic review of modafinil for fatigue (65 reviews) | 60% positive experience, 22% negative; average fatigue rating 6.9/10 |
| Meta-analysis of adverse events in major depressive disorder | Higher risk of anxiety/nervousness in off-label users (RR 1.95) versus placebo |
Effect on anxiety
The potential for anxiety exacerbation is the most prominent concern for patients with pre-existing anxiety disorders. Systematic review and meta-analysis findings indicate that, while modafinil may offer mood-elevating effects in some, it can also elevate negative affect. Reports in user communities suggest the anxiety often manifests as a “revved up” feeling or a sense of dread, particularly in the initial days of treatment. It is also noteworthy that for some, the anxiety effect may diminish with continued use.
The recommendation to start low and titrate slowly
A recommendation to start with a quarter of a 100 mg tablet (25 mg) is clinically sound and supported by the evidence. Starting at a subtherapeutic dose allows assessment of individual sensitivity to the drug's anxiogenic potential and other side effects before titrating to an effective dose.
This cautious approach is reinforced by the known risks. While modafinil is considered relatively safe, it is not without significant psychiatric risks. A 2026 systematic review of modafinil-associated psychosis found that cases occurred across a wide diagnostic range and sometimes at therapeutic doses. The most common symptoms were hallucinations (66.7%) and delusions (58.3%). While these events are rare, the review recommends caution in patients with comorbid psychiatric conditions.
the literature clearly documents the potential for modafinil to provoke or worsen anxiety and, in rare cases, precipitate psychosis.
A note on the Australian context
Location is relevant to treatment pathway. While the Australian PBS subsidises modafinil for narcolepsy and sleep apnoea, access can be more complex for a diagnosis of IH, though many doctors submit applications using narcolepsy criteria to secure approval. Consultation with a psychiatrist is an appropriate step given the complex interplay of IH and mood disorders.
Conclusion
For patients with a history of anxiety and depression, initiating modafinil for idiopathic hypersomnia requires a careful, evidence-based approach. The drug may offer significant benefits by alleviating the profound sleepiness that can drive or exacerbate mood disturbance. However, the literature also clearly documents the potential for modafinil to provoke or worsen anxiety and, in rare cases, precipitate psychosis.
The most prudent strategy is conservative: starting at the lowest possible dose (for example 25 mg), closely monitoring for any increase in anxiety or depressive symptoms, and titrating upwards only if tolerated.
