The proof that modafinil helps depersonalization disorder is thin, but there are glimpses of hope that it may aid in treating the disorder.
The first comes from this study, “Potential Uses of Modafinil in Psychiatric Disorders“.
The study used modafinil on patients with a very broad range of disorders, including depersonalization disorder. Impressively, 84.4% of patients showed an improvement of their scores with modafinil.
Other scientists are also positive about the effect modafinil may have on depersonalization disorder. A review of the book Feeling Unreal in The British Journal of Psychiatry states:
Depersonalisation disorder is notoriously resistant to treatment but promising results are claimed for treatment with either lamotrigine, the combination of a selective serotonin reuptake inhibitor antidepressant and the stimulant modafinil, or opioid antagonists, but there are few controlled trials.
Lastly, modafinil has shown benefits in the treatment of Kleine-Levin syndrome, and Kleine-Levin syndrome has been linked to depersonalization disorder. In “Klein-Levin syndrome: a review“, the authors state:
Kleine-Levin syndrome, while rare, is often misdiagnosed or unrecognized, and should be considered in any teenager presenting with recurrent episodes of hypersomnia concurrent with cognitive changes, depersonalization, or disinhibition.
So, this very thin evidence may not be much to hang our hats on, but it and first-hand reports are all we have to go off until a proper trial is conducted.