Background: The aim of this research was to evaluate an online exposure treatment for spider phobia (www.feardrop.com) and to investigate the effects of intermittent versus continuous exposure.

Methods: Spider phobic participants (N = 23) completed two 14-minute stages of laboratory-based online exposure. In the first of these stages exposure was either continuous or intermittent (alternating fearrelevant and -irrelevant images). One week later, participants commenced a sixstage home-based graded online exposure task, which was undertaken over 30 days. Subjective Units of Distress Scale (SUDS) ratings were taken throughout all exposure stages. Spider fear was assessed prior to treatment, and at 1-week and 1-month post treatment.

Results: Habituation was observed across each stage for both the laboratory and home-based tasks and generalisation of habituation was found between stages. Habituation was not impaired in the alternating fear-relevant and -irrelevant image condition, though subjects experienced less summed anxiety. Adherence rates were low in home-based online exposure. However, participants who completed 30-days post-treatment assessment (n = 14) showed a significant reduction in spider fear as measured by the Fear of Spiders Questionnaire (FSQ).

Conclusions: Online exposure produces habituation and generalisation of habituation to spider images as well as longer-term reductions in spider fear. Alternating fear-relevant and -irrelevant exposure is feasible in online exposure and may lead to habituation with less summed anxiety that has implications for tolerability and acceptability. Measures to increase adherence rates and hence dosage delivered are a key consideration for further online exposure research.