Re-encountering the phobic cue within days after a reconsolidation intervention is crucial to observe a lasting fear reduction in spider phobia.

Memory reconsolidation interventions offer an exciting alternative to exposure treatment because they may target fear memories directly, thereby preventing relapse. A previous reconsolidation intervention for spider fear abruptly reduced avoidance behaviour, whereas changes in self-reported fear followed later. In this pre-registered placebo-controlled study, we first aimed to conceptually replicate these effects in spider phobia. Second, we investigated whether re-encountering the phobic cue after the reconsolidation intervention is necessary for changes in self-reported fear to occur. Third, we tested whether the window to trigger such changes is time limited. Individuals with spider phobia (N = 69) were randomized into three groups and underwent a memory reactivation procedure with a tarantula, followed immediately by propranolol (reconsolidation intervention) or placebo. One reconsolidation intervention group and the placebo group re-encountered spiders two days after treatment in behavioural approach tasks, whereas another reconsolidation intervention group re-encountered spiders after four weeks. Changes in spider avoidance behaviour and self-reported fear were followed for one year. In the short term, the reconsolidation intervention was not more effective than placebo: both conditions benefited from the intervention. In the long term, the reconsolidation intervention was more effective than placebo, but only when the phobic stimulus was re-encountered within days after treatment. Specifically, we found less tarantula avoidance behaviour and self-reported fear over the course of one year when spiders were re-encountered two days after the reconsolidation intervention, but not when the behavioural test was conducted four weeks after the intervention. These findings challenge the idea that a reconsolidation-inspired intervention alone is sufficient to treat clinical fears: Experiencing the behavioural change during the re-encounter within days after the reconsolidation window has closed seems crucial to observe a lasting fear reduction.