Investigating anxiety and depression in adults with low intellectual ability

© 2016 Dr. Stephen Langley EdwardsAdults with low ability have been routinely excluded from general population research that supports cognitive behavioural therapy for anxiety and depression. Even studies using samples of adults with ability below average exclude potential participants with profound and severe intellectual disability, without testing task-specific capacity. Consequently, little is known about the viability of cognitive models of anxiety and depression amongst adults with low ability. The present study addresses this through four main lines of enquiry: inclusion of all abilities through screening and validity procedures; prevalence of signs and symptoms of anxiety and depression as well as the impact of life stressors on these; cognitions and their specificity for anxiety and depression; and the impact of anxiety and ability on attentional responses to emotional stimuli. A sample of 70 adults from each level of low ability, unselected for signs or symptoms of anxiety and depression, was recruited from community-based disability support services. Participants were screened for general (receptive language) and task-specific abilities, interviewed for symptoms of anxiety and depression and disorder related cognitions then administered a visual-probe task with emotional face stimuli. Informants provided data on signs of mental ill-health, stressful life events and adaptive behaviour. Task-specific validity procedures governed data included for analysis. The inclusionary approach meant participants from all ability levels below average were included. Task-specific screening measures were superior to receptive language in predicting validity on research tasks, especially for participants with severe and profound intellectual disability. Dimensional measurements meant ability variables could be covaried or controlled in most analyses. Mean levels of signs and symptoms were lower than those in available reference studies, as were the rates of clinical level cases. General ability was positively correlated with signs of anxiety and depression but was not related to symptoms. Similarly, the number of life events was correlated with all scales on the measure of signs but not with symptoms of anxiety or depression. The lack of concordance highlights the gap between what informants see and what respondents think and feel. Learning a person’s subjective interpretation of events can help understand their emotions and behaviour. Depressive cognitions uniquely predicted significant variance in symptoms of depression but only ability, rather than anxious cognitions, predicted anxiety symptoms. Cognitive content-specificity for depression bolsters support for the use of cognitive behaviour therapy but further research into the relationship between ability and anxiety is required. The lack of directional bias in selective attention to emotional faces in any of the anxiety or ability groups means cognitive-motivational theory was not supported but future studies should address methodological issues. Attentional control theory was supported but the slowing of emotional face processing caused by high anxiety, but not depression needs replication. Trials of attentional training may be justified to reduce anxiety. Further research into cognitive models of anxiety and depression is urgently needed and future studies should ask theoretical as well as clinical questions