Theory of Mind Decoding and Reasoning Abilities in Depression, Social Phobia, and Comorbid Conditions

Abstract

Vulnerability to major depressive disorder (MDD) is characterized by extensive interpersonal dysfunction. A framework that has been used to understand this impairment is theory of mind, or the ability to decode and reason about others’ mental states. Previous research has identified a mental state decoding advantage in individuals with a past history of MDD, which has been explained in terms of an enhanced social orientation in those with depression vulnerability. Although social phobia is highly comorbid with MDD, there is no research investigating theory of mind abilities in individuals with social phobia, nor has there been research examining how social anxiety may better account for the relation of depression to heightened theory of mind ability. Furthermore, there is a paucity of research investigating whether evidence of such a relation extends to the more complex task of reasoning about others’ mental states. Thus, the goals of the current investigation were to examine whether heightened ToM accuracy in those with a history of MDD is better accounted for by social phobia, and whether superior ToM skills in those with past MDD are seen across tasks that tap the domains of decoding and reasoning. Participants (N = 109) were assigned to one of four groups based on a structured diagnostic interview: (a) past MDD only (n = 36); (b) social anxiety disorder only (n = 9); (c) comorbid past MDD and social anxiety disorder (n = 23); and (d) no psychiatric history (n = 41). Results show that having a history of MDD is associated with heightened mental state reasoning abilities only in the presence of current social phobia. However, theory of mind decoding was not elevated in this condition. This suggests that social phobia differentially influences the relation of past MDD and theory of mind ability for decoding and reasoning abilities. Furthermore, social phobia without a history of depression was associated with poor theory of mind decoding and reasoning. This reduced ability in individuals with social phobia may be the result of self-focused attention or avoidance of potential negative evaluation, but future research is required to specifically address these possibilities.