Schematic beliefs and problem solving performance predict depression in people experiencing persecutory delusions

Abstract

Depression occurring alongside psychosis is an important treatment target, both in its own right and as a potential maintenance factor for positive psychotic symptoms. The present paper reports a prospective longitudinal analysis of depression and its predictors over six months in a group of 60 participants experiencing persecutory delusions. We hypothesised that negative schematic beliefs about the self and problem solving difficulties would predict the persistence of depression over time. The results showed, as hypothesised, that more negative schematic beliefs about the self and poorer problem solving predicted higher depression scores six months later, beyond what could be predicted by baseline depression scores. These findings support a proposed role for schematic beliefs and problem solving difficulties in the perpetuation of depression occurring alongside psychosis, as has been substantiated for major depressive disorder. Interventionist research is warranted to confirm causal effects.

Introduction

Depression is known to be common among people with persecutory delusions (Vorontsova et al., 2013). The importance of such depression as a treatment target in its own right is supported by its associations with suicide, low quality of life, functional impairment and future relapses (Conley et al., 2007). Freeman and colleagues argued that depression also acts as a key maintenance factor for persecutory delusions (Freeman et al., 2002). This theory is substantiated by empirical findings that depression predicts the persistence of paranoia over time (Fowler et al., 2012, Vorontsova et al., 2013). Amelioration of comorbid depression is therefore also a potential therapeutic target in the treatment of persecutory delusions. An improved understanding of what maintains depression in this group will facilitate development of therapies to treat it, which has the potential to also impact the course of delusions, as well as improving functional outcomes.

Several cognitive factors have established associations with the persistence of major depressive disorder: a summary may be found in Vorontsova et al. (2013). Two factors were of particular interest in the present study: negative schematic beliefs and problem-solving difficulties. As we discuss below, each of these plays a plausible theoretical role in the perpetuation of depression, each has shown associations with the persistence of symptoms, and each has links to a targeted evidence-based therapeutic intervention.

Negative schematic beliefs about the self lie at the heart of cognitive theories of depression, and are proposed to perpetuate negative affective states by colouring the interpretation of ongoing experience (Beck, 1979, Clark and Beck, 1999). Interventions targeting beliefs about the self have shown evidence of effectiveness in ameliorating depression in groups of people experiencing psychosis (Freeman et al., 2014, Hall and Tarrier, 2003, Knight et al., 2006, Laithwaite et al., 2007), with two pilot studies finding concomitant effects on delusion severity (Freeman et al., 2014, Laithwaite et al., 2007).

Problem solving difficulties characterise groups with depression compared to non-clinical controls (Marx et al., 1992), and have been shown to predict the persistence of depression over time (Garland et al., 2000). Problem solving difficulties are thought to perpetuate depression by limiting an individual's effectiveness in tackling every-day challenges. Improvements in performance have been achieved with problem solving therapy, which has shown effectiveness in ameliorating depression (Bell & D'Zurilla, 2009).

Vorontsova et al. (2013) examined schematic beliefs and problem solving difficulties in a prospective longitudinal study of 60 individuals experiencing persecutory delusions. Negative schematic beliefs about the self and problem solving difficulties each significantly predicted the persistence of paranoia over six months, with baseline paranoia controlled. The present paper presents a previously unpublished secondary analysis of data from the same study, with novel hypotheses concerning the prediction of depression persistence. Given the reciprocal relationship between paranoia and depression, it is expected that some of the same factors could contribute to the persistence of both difficulties (Moritz et al., 2017, Zavos et al., 2016). We therefore hypothesised that more negative beliefs about the self and poorer problem solving performance would predict higher depression scores at six-month follow-up, with baseline depression scores controlled.