Chronic Postconcussive Headache: A Placebo-Controlled Treatment Trial of Prazosin

Inclusion Criteria: * Veterans or active duty service members aged 18 or older of either gender * Good general health * History of blast and/or impact head/neck trauma meeting DVBIC criteria for mild TBI, i.e., injury as manifested by at least one of the following: * 1\) any period of loss of consciousness * 2\) any loss of memory for events immediately before or after the accident * 3\) any alteration in mental status at the time of the accident (e.g., feeling dazed, disoriented, or confused) * 4\) focal neurological deficit(s) that may or may not be transient, with severity of injury not exceeding loss of consciousness 30 minutes, Glasgow Coma Scale \<13-15 after 30 minutes, or posttraumatic amnesia \>24 hrs, * Headaches that started within 3 months of a head/neck injury or pre-existing headaches that markedly worsened (by a two-fold or greater increase in frequency and/or severity) within 3 months of a head/neck injury. Headaches must either 1) last 4 or more hours a day and reach a moderate to severe intensity at any point during the headache or 2) may be of any severity or duration if the participant uses a medication or other agent in an effort to stop the headache. Headaches meeting these criteria must have been present on average at least 8 days per 4-week period over the 3 months preceding study enrollment. * Comorbid PTSD or other anxiety disorder is not exclusionary. * Fluency in English is required. * Persons of all races and ethnicities are eligible. * Female participants must agree to abstain from sexual relations that could result in pregnancy or use a reliable form of birth control during the study. * Continued use of prophylactic migraine medication other than the study drug is permissible if the participant has been on a stable dose for at least 4 weeks prior to the preliminary screening period and intends to continue the medication for the duration of the trial. Exclusion Criteria: * Participation in other interventional research. * History of TBI more severe than that classified as mild by DVBIC criteria * A primary non migraine and/or tension-type headache disorder that accounts for the majority of current symptoms * History of penetrating head injury * Headaches of any kind of moderate or severe intensity on an average of more than 4 days per month preceding the concussive trauma * Acute or unstable chronic medical illness (e.g., unstable angina, myocardial infarction within 6 months, congestive heart failure, symptomatic or concernin…