Effects of Ecopipam or Placebo in Adults With Stuttering (Speak Freely)

Inclusion Criteria: * Able to read and write in English and provide informed consent * 18 years or older of age at screening * Weighs \>= 45 kg (\~99 lbs) * Satisfies DSM-5 criteria for childhood onset fluency disorder * History of stuttering for \>=2 years with onset consistent to developmental in nature * Must meet an allowed severity of stuttering at screening and baseline, scored by a central rater * Completed an adequate course of speech therapy * Has a qualifying IOS or Android smartphone * Must discontinue all medications used to treat stuttering for at least 14 days prior to screening * Sexually active females of child bearing potential must be using effective contraception during and 30 days after participation * Sexually active males must use a double barrier method of contraception during and 30 days after participation Exclusion Criteria: * Stuttering is related to a known neurological cause * Initiation of new behavioral therapies for stuttering within 10 weeks prior to baseline * Unstable medical illness or clinically significant abnormalities on screening tests/exams * At a significant risk of committing suicide * Are pregnant or lactating * Positive urine drug screen * Lifetime history of major depressive episode * History of seizures * Have been previously treated with ecopipam * Unstable use of medications prior to screening * Use of prohibited medications or need for medications which would have unfavorable interactions with ecopipam * Not suitable for study in the opinion of the Principle Investigator