This study investigates whether a one-session exposure treatment for spider-related stimuli can lead to a generalization of extinguished fear to height-related stimuli in individuals with comorbid fear of spiders and fear of heights.

Exposure therapy has been proven to be effective in the treatment of specific phobias and in a variety of fear evoking situations and stimuli. However, since there is a high prevalence of comorbid fears, therapeutic interventions can get very extensive when each fearful situation and / or stimuli needs to be treated separately and over a repeated number of times. It has recently been shown, that exposure to one fearful stimuli (i.e., a spider), can also lead to a reduction of fear to another, perceptually and conceptually related, but untreated fearful stimulus (i.e., a cockroach) (Preusser, Margraf & Zlomuzica, 2017). Potentially, this generalization of exposure effects might also be relevant for coexisting fears that do not share conceptually related fearful stimuli (e.g., fear of spiders and fear of heights). The present study aims to investigate whether successful exposure treatment to one fearful stimulus (i.e., a spider) can also lead to a reduction of fear to an untreated fear evoking stimulus (i.e., height).

Participants will be randomly assigned to the treatment or no-treatment condition. The entire experimental procedure will take place in three sessions. The first session incorporates spider and height fear related questionnaires and two Behavioral Approach Tests (BATs): One that involves a spider and one that involves height. These BATs are counterbalanced in each group with half of participants receiving the spider BAT first and the height BAT second, and vice versa. The second session takes place approximately seven days later. The treatment group receives a seven-step in vivo exposure with spiders (duration: 1,5 hours). Twenty-four hours later, session 3 takes place and involves the same measures that were applied in session 1. The treatment and no-treatment group receive an identical set of measures except that the no-treatment group will not be subjected to exposure. The effects of exposure-based anxiety reductions toward spiders (treated fear stimulus) and heights (untreated fear stimulus to assess generalization of treatment outcome) are assessed on the behavioral and subjective level at pretreatment and posttreatment (24 hours after exposure).

Inclusion Criteria:

• Comorbid presence of fear of spiders and fear of heights [Potential diagnosis of specific phobias (arachnophobia and acrophobia) assessed by application of the Diagnostic Short-Interview for Mental Disorders (Mini-Dips)].

Exclusion Criteria:

• Any acute or chronic mental and / or somatic disease
• Psychological, psychiatric, neurological or pharmacological treatment (Application of the Mini-DIPS to screen for the presence of a psychological condition)
• Drug or alcohol abuse
• Pregnancy