Can Modafinil Make You Irritable?
Yes. Irritability can occur with modafinil, although larger controlled safety studies more consistently report nervousness, anxiety and insomnia.[1,2]
Direct evidence for irritability comes from a small controlled study in healthy volunteers, while high-dose clinical experience and psychiatric case reports provide additional evidence that mood and behavioural changes can occur.[1,3,4]
Is Irritability a Common Side Effect of Modafinil?
In pooled safety data from six randomised, double-blind, placebo-controlled studies, irritability was not identified among the common treatment-emergent adverse events associated with modafinil.[2]
Roth et al. analysed 1,501 participants who received at least one study dose, including 934 treated with modafinil and 567 given placebo. Among those receiving modafinil, nervousness occurred in 7%, while anxiety and insomnia each occurred in 5%.[2]
Similarly, the current Provigil prescribing information states that psychiatric symptoms leading to treatment discontinuation more often with modafinil than placebo included anxiety, nervousness, insomnia, confusion, agitation and depression, but not irritability.[3]
A 2026 systematic review and meta-analysis of 54 studies also found increased risks of anxiety or nervousness in several populations treated with modafinil, including people with obstructive sleep apnoea, shift work sleep disorder and major depressive disorder. Irritability was not analysed as a separate adverse-event outcome.[5]
What Did the Study That Measured Irritability Find?
Randall et al. studied 30 healthy university students who were not sleep deprived. Participants were randomly assigned to receive placebo, 100 mg of modafinil or 200 mg of modafinil in a double-blind design.[1]
Three hours later, they completed visual analogue scales assessing mood and physical symptoms before and after cognitive testing. Individual ratings showing significant post-treatment changes included irritability, restlessness, muscular tension, shaking, palpitations, dizziness and physical tiredness.[1]
The researchers also found a significant change in a broader measure of somatic anxiety, with the main effect driven by higher somatic-anxiety ratings in the 100 mg group.[1]
Because the participants were healthy and not sleep deprived, the study was less affected by underlying sleep disorders or acute sleep loss as alternative explanations for changes in mood.
However, the study included only 30 participants and examined responses after a single dose, so it cannot establish how frequently clinically meaningful irritability occurs during longer-term modafinil treatment.
The results also did not show a straightforward dose-response pattern, with the broader mood effect more apparent in the 100 mg group than in the 200 mg group.[1]
Can High Doses of Modafinil Cause Irritability?
The Provigil prescribing information describes protocol-specified modafinil doses ranging from 1,000 to 1,600 mg per day during clinical studies. Thirty-two people received 151 such doses, and 13 participants received either 1,000 or 1,200 mg per day for 7 to 21 consecutive days.[3]
Effects observed during high-dose clinical experience included irritability, aggressiveness, anxiety, nervousness, confusion, excitation or agitation, insomnia, tremor, palpitations and other sleep disturbances.[3]
These exposures were substantially higher than the recommended 200 mg daily dose for narcolepsy, obstructive sleep apnoea and shift work sleep disorder.[3]
They should not be interpreted as showing that irritability occurs at the same frequency during ordinary therapeutic use or that it increases predictably as therapeutic doses rise.
Therapeutic-dose data do not show the same pattern. In Roth et al.’s pooled trials using 200, 300 or 400 mg per day, headache was the only adverse event identified as having a statistically significant dose-related trend.[2]
What About Irritability in People With a Psychiatric History?
Ranjan and Chandra described irritability and aggression in two patients with bipolar disorder taking modafinil, although a two-patient case report cannot establish how frequently this occurs or predict the response of people with bipolar disorder generally.[4]
Postmarketing psychiatric reactions associated with modafinil have included mania, delusions, hallucinations, suicidal ideation and aggression. Many, but not all, of the affected patients had a previous psychiatric history.[3]
The prescribing information advises caution when modafinil is given to people with a history of psychosis, depression or mania and recommends considering discontinuation if psychiatric symptoms develop.[3]
This does not mean someone with a psychiatric history will become irritable while taking modafinil, only that substantial new changes in mood or behaviour warrant clinical attention.
Are Anxiety, Nervousness and Irritability the Same Thing?
No. Clinical studies record anxiety, nervousness, agitation and irritability as separate adverse events.
Large modafinil safety studies report anxiety, nervousness and insomnia more consistently than irritability, but those terms should not be treated as interchangeable.[2,5]
A clinical trial reporting a certain frequency of anxiety or nervousness therefore cannot be used to estimate the frequency of modafinil-induced irritability.
What Should You Do If Modafinil Makes You Irritable?
Persistent or worsening irritability after starting modafinil or changing treatment should be discussed with the prescribing clinician, particularly if the change is unusual or begins to affect behaviour, relationships or daily functioning.
If modafinil has been prescribed, do not take more than prescribed or change the dosing schedule without medical advice. MedlinePlus also advises patients not to stop modafinil without discussing it with their doctor.[6]
Mild irritability is different from a substantial psychiatric reaction. The prescribing information warns about reactions including mania, hallucinations, delusions, suicidal ideation and aggression.[3]
MedlinePlus advises contacting a doctor immediately for symptoms including an abnormally excited mood, hallucinations, anxiety, depression or thoughts of harming or killing yourself.[6]
References
- Randall, D. C., Shneerson, J. M., Plaha, K. K., & File, S. E. (2003). Modafinil affects mood, but not cognitive function, in healthy young volunteers. Human Psychopharmacology: Clinical and Experimental, 18(3), 163–173. https://doi.org/10.1002/hup.456
- Roth, T., Schwartz, J. R. L., Hirshkowitz, M., Erman, M. K., Dayno, J. M., & Arora, S. (2007). Evaluation of the safety of modafinil for treatment of excessive sleepiness. Journal of Clinical Sleep Medicine, 3(6), 595–602.
- U.S. National Library of Medicine. (2025). Provigil (modafinil) tablet [Prescribing information]. DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=0391f182-1958-9fef-a944-53b229ce99e7
- Ranjan, S., & Chandra, P. S. (2005). Modafinil-induced irritability and aggression? A report of 2 bipolar patients. Journal of Clinical Psychopharmacology, 25(6), 628–629. https://doi.org/10.1097/01.jcp.0000185346.77966.a4
- Jung, J., Youm, J., Kang, J., Kim, A.-Y., Suh, J. K., & Kang, H.-Y. (2026). Assessing condition-specific adverse event profiles of modafinil for labelled and off-label uses: A systematic review and meta-analysis. Basic & Clinical Pharmacology & Toxicology, 138(1), e70147. https://doi.org/10.1111/bcpt.70147
- U.S. National Library of Medicine. (2024). Modafinil: MedlinePlus drug information. MedlinePlus. https://medlineplus.gov/druginfo/meds/a602016.html
