Global functioning is a measure of the severity of mental illness that provides an overall picture of a person’s combined psychological, social, and occupational functioning, and reveals how well or otherwise they are dealing with social and interpersonal problems. Poor functioning has been reported in individuals with schizophrenic spectrum disorder (SSD) and autistic spectrum disorder (ASD), and so you would expect an even worse outcome in bipolar disorder (BD) patients with high levels of co-occurring autistic and mild psychotic traits (schizotypy).
In a study by Abu-Akel, Wood, Hansen, and Apperly, which evaluated the effect of co-occurring autistic and psychotic traits on the ability to appreciate others’ point of view—a key component of normal mentalizing. It showed that while autistic and schizotypal traits independently induced perspective-taking errors, their interaction was associated with fewer errors, reflecting an improvement in mentalizing abilities.
The authors proposed that this unexpected finding may be explained by the diametric model, which postulates that ASD and SSD/psychotic spectrum disorders have opposing effects on mentalizing abilities, whereby autism is associated with reduced or no mentalizing, and psychosis with dysfunctional hyper-mentalizing. To date, no study has investigated the effect of co-occurring autistic and schizotypal traits in a psychiatric population on an outcome of clinical significance, such as global functioning.
But now a new study by Ahmad Abu-Akel and eight colleagues sets out, first to determine the expression of autistic and positive schizotypal traits in a large sample of adults with BD, and then to examine whether co-occurring autistic and positive schizotypal traits interact to affect global functioning. The subjects were 797 participants with DSM-IV bipolar I disorder who completed measures of both autistic spectrum and schizotypal traits.
Approximately half of the sample exhibited clinically significant levels of autistic traits, and over a third did when applying a more exacting criterion. This is consistent with the single previous study of autistic-like traits in adults with BD, which found that half of the participants demonstrated high levels of autistic-like traits.
Analysis of both individual differences and group similarities provided evidence that both autistic and positive schizotypal traits were associated with better global functioning, with their effects being best when both traits were high rather when both were low:
As the authors point out, the mechanism by which this takes place is currently unknown. However, the pattern of the interactive effect of autistic and schizotypal traits on global functioning during the worst depressive episode suggests that the effect of the expression of one condition depends on the relative expression of the other, and that these traits may be interacting in a compensatory manner to improve global functioning (below).Specifically, during the worst episode of mania, the individual differences analysis showed that both autism traits and positive schizotypal traits independently contributed to increased global functioning. This was consistent with the results from the group analysis, which showed that the functioning of the high autism, high positive schizotypal group were significantly better than the other groups during the worst episode of mania even after controlling for potential confounders. During the worst episode of depression, individual differences analysis showed that autistic and positive schizotypal traits were interactively associated with increased global functioning.
Source: Journal of Affective Disorders 207 (2017) 268–275
A previous study by Abu-Akel and others found that distinct mechanisms of attention might be at work that are differentially affected in autism as opposed to psychosis, “anti-correlated,” cerebral networks have recently been associated with autistic-like, mechanistic cognition as opposed to mentalizing which might conceivably be the basis for this in the brain. Indeed, an even more recent study which was not looking for it reported not only “a robust, heritable, specific, and behaviourally relevant reduction” in the mentalizing (default mode) network “across the autism spectrum,” but the opposite in a control group of patients suffering from depression.
This is all exactly as the diametric model of the mind and of mental illness would predict (above). Furthermore, the fact that both SSD and ASD lie at the extremes of a continuum implies that normality lies in between and could be seen as the result of both tendencies cancelling each other out, just as this study discovered in BD. Indeed, you could say that being normal means being autistic enough not to be psychotic, and being psychotic enough not to be autistic!
(With thanks to Ahmad Abu-Akel and Amar Annus for their help.)