Planning Skills in Autism Spectrum Disorder Across the Lifespan: A Meta-Analysis and Meta-Regression

Background: Planning is an important part of life as it both directs and evaluates the strategy we use to reach our pre-specified goals. People with autism spectrum disorder (ASD) are thought to encounter difficulty with planning. Experimental research, however, lacks consensus on the mastery of this skill in ASD. The last, narrative, review on this topic dates back to 2004 and concluded that people with ASD have planning difficulties and that age might influence planning (Hill, 2004). To date, however, the literature on planning in ASD has not been quantitatively reviewed, and still little is known about possible age-related effects on planning in ASD. 

Objectives: By means of a meta-analysis and meta-regression, we aim to conceptualize (1) the magnitude of possible planning deficits in ASD; (2) potential age-related effects on planning; (3) which of the array of planning measures is most consistent in its findings; (4) whether intelligence levels have an effect on planning. 

Methods: A systematic literature search identified 49 eligible studies with a combined sample size of 1737 people with ASD and 1600 typically developing (TD) controls (mean age range: 4.9-63.6 years). For each continuous outcome, a Hedges’ geffect size was calculated. A positive effect size indicated poorer planning by the ASD group as compared to the TD group. Next, a random-effects meta-analysis was performed, followed by meta-regression techniques to examine moderating effects of age, type of task and IQ. 

Results: The preliminary meta-analysis indicated that individuals with ASD perform worse on planning tasks as compared to TD controls (effect size 0.53). Age and type of task did not seem to have an effect on planning. IQ was a relevant moderator (explaining 31.25% of the total heterogeneity), with smaller effects with increasing IQ. The residual heterogeneity between studies remained large and significant. Investigation of publication bias suggested missing studies with a negative effect. Although inclusion of these hypothetical studies would decrease overall mean effect size, the effect size would remain significant. 

Conclusions: Our preliminary results of this meta-analysis on planning performance in ASD showed that people with ASD have indeed difficulty with planning. Furthermore, it showed that age does not moderate effects, while IQ does. However, a large amount of variation between studies remained unexplained. Thus, while people with ASD have planning problems across the lifespan, there are additional factors that influence their planning performance that need to be considered in future studies.