The purpose of this study is to evaluate whether valproic acid in combination with fear memory reactivation is useful to enhance treatment stability of exposure therapy for specific phobia.

• There will be one screening visit (visit 1), one intervention visit (visit 2) and one follow-up visit (90 days after visit 2) (visit 3).
• On visit 2 all participants will undergo 30 min exposure therapy in virtual reality with pre-defined spider situations.
• Duration for an individual participant will be at most 15 weeks depending on the time passing between screening (visit 1) and intervention visit (visit 2).
• Change in phobic fear to baseline (visit 1) will be assessed on 90 day follow-up (visit 3).
• Documentation of all study relevant source data of every study participant will be done by completing the study specific electronic case report forms (eCRF, SoSci Survey) and study specific case report forms on paper (Adverse Events, Serious Adverse Events and concomitant medication). Data in the eCRF can be validated for completeness and discrepancies automatically. An audit trail system maintains a record of initial entries and changes (reasons for changes, time and date of changes, user identification of entry and changes).
• Quality insurance will be done by an external site monitoring (including study progress, accuracy and completeness of eCRF, fulfillment of protocol requirements, applicable local authority regulations and investigator's obligations).
• Monitoring includes 100% of safety parameters, primary endpoints, informed consent documents and the Trial Master File on the Initiation Visit and on Close Out.
• Standard Operating Procedures to address study activities such as patient recruitment, informed consent, study interventions, data collection, data management, data analysis, and reporting for adverse events exist.

Inclusion Criteria:

• DSM-IV diagnosis of specific phobia (animal type: spider)
• BAT score (at screening) between 1 and 7 points
• Physically healthy
• Normotensive (90/60-140/90 mmHg)
• Male or female
• Aged between 18 and 40 years
• Native or fluent German-speaking
• Females have to be on effective birth control

Exclusion Criteria:

• Other axis I disorder except a further comorbid phobic disorder
• Concurrent psychotherapy or pharmacotherapy
• Previous exposure-based therapy for specific phobia
• Parallel participation in another study
• Body weight less than 50kg
• Long-term medication intake
• Substance abuse
• 5 or more cigarettes a day and/or inability of being abstinent for at least 5 hours
• Pregnancy or breast-feeding
• Kinetosis
• History of coagulation disease
• History of gastrointestinal disease
• Laboratory exclusion criteria: clinically relevant deviation of laboratory values (blood count, blood chemistry, coagulation status, liver and pancreas enzymes, electrolytes) from normal range