Sleep's Influence on the Treatment of Intrusive Emotional

Inclusion Criteria: * DSM V criteria of PTSD (at least moderate symptoms in two categories) * Currently receiving Written Exposure Therapy at one of the psychotherapy centers at the Psychiatric University Clinic (PUC). * Not more than moderate alcohol consumption (not more than 5 alcoholic drinks/week). * Ability to understand the study instructions Exclusion Criteria: * Travel over \> 3 time zones in \< 3 months * head injury * shift work * current substance abuse * neurological disease * drug addiction * Current suicidality Specific exclusion criteria for the fMRI: * Acute psychotic symptoms * Pregnancy * Claustrophobia * Magnetic resonance imaging incompatibility: * Cardiac pacemaker or other metallic implants (e.g. metallic cardiac valve, insulin pump) * Metallic foreign particles (e.g. after bullet wound, shell splinter, clips, metal prostheses)