Intrusive memories of traumatic events are core features of posttraumatic stress disorder (PTSD) but little is known about the neurobiological formation of intrusions. The aim of this study was to determine whether the activity of the noradrenergic system during an intrusion-inducing stressor influences subsequent intrusive memories.

The investigators conducted an experimental, double-blind, placebo-controlled study in 118 healthy women. Prior to watching an established trauma film paradigm that induces short lasting intrusions, participants received a single dose of either 10 mg yohimbine, stimulating noradrenergic activity, or 0.15 mg clonidine, inhibiting noradrenergic activity, or placebo. The number of consecutive intrusions of the trauma film, the mean vividness of the intrusions and the mean degree of distress evoked by the intrusions were assessed during the following four days. Salivary cortisol and alpha-amylase were collected at seven time points prior to, and after the trauma film.

Inclusion Criteria:

• healthy participants
• German on a native level

Exclusion Criteria:

• former or present DSM IV Axis I disorders
• physical illnesses
• any medication intake (except oral contraceptive)
• history of sexual abuse or rape
• pregnancy or lactation period