Acceptance and Commitment Therapy-based Rehabilitation of Post-concussion Symptoms

The investigators aim to evaluate effects of an outpatient rehabilitation program based on Acceptance and Commitment Therapy compared to usual care on function in patients with post-concussion syndrome (PCS) and post-traumatic headache (PTH). This study builds on the investigators' previous observational studies and treatment studies in this patient group.

Inclusion Criteria: * Having sustained a minimal HI or MTBI * PCS/ PTH had evolved within 1 week after the head trauma. * At least one post-concussion symptoms of at least moderate degree, that affects daily life. * \> 6 months post-injury. * First line treatment has been tried, e.g. psychoeducation, increase of physical activity and pharmacological treatments for headache Exclusion Criteria: * More than 5 years since last injury. * Symptoms are better explained by other conditions. * Severe communication problems, typically due to poor knowledge of Norwegian. * Severe psychiatric, neurological, somatic or substance abuse disorders that will make it problematic to function in a group and/or will complicate follow-up and outcome assessment.