Which of the following components of the neuron is most pertinent to the study of abnormal behavior?

Psychological therapies, such as cognitive behavioral therapy, have advanced through increased knowledge of the psychological processes that maintain and exacerbate mental health problems (Beck & Haigh, 2014; Harvey, Watkins, Mansell, & Shafran, 2004; Salkovskis, 2002). Many of these processes were initially studied in anxiety disorders (e.g. selective attention to threat – MacLeod & Mathews, 1988; safety-seeking behaviors – Salkovskis, 1991). Yet, for over a decade now, it has been established that the majority of maintenance processes are shared by a diverse range of psychological disorders, i.e. they are ‘transdiagnostic’ (Harvey et al., 2004). In tandem with this evidence, there is a compelling argument that transdiagnostic psychological interventions are likely to be more practical and efficient to train and deliver (Mansell, Harvey, Watkins, & Shafran, 2009; McHugh, Murray, & Barlow, 2009). To complement this rationale, reviews and meta-analyses have found evidence for their efficacy in treating symptoms (McEvoy, Nathan, & Norton, 2009; Newby, McKinnon, Kuyken, Gilbody, & Dalgleish, 2015).

Despite the burgeoning of scientific interest in the transdiagnostic approach, the theoretical underpinnings of the approach are diverse and there is little consensus (Cowdrey, Lomax, Gregory, & Barnard, 2016; Mansell et al., 2009). Moreover, with over twenty different potential transdiagnostic processes identified to date, we are left with two alternatives – (a) to combine many of the processes within a single model that is consistent with existing cognitive behavioral models (e.g. McManus, Shafran, & Cooper, 2010) or (b) to identify one core process that is the focus of a transdiagnostic intervention, such as experiential avoidance (Spinhoven, Drost, de Rooij, van Hemert, & Penninx, 2014), metacognition (Wells & Matthews, 1994), repetitive negative thinking (McEvoy, Erceg-Hurn, Anderson, Campbell, Swan et al., 2015; McEvoy, Erceg-Hurn, Anderson, Campbell, & Nathan, 2015), distress tolerance (Bardeen, Fergus, & Orcutt, 2013), or intolerance of uncertainty (McEvoy & Mahoney, 2012; Mahoney & McEvoy, 2012). In choosing between these alternatives, it is vital to entertain the possibility that there is considerable conceptual, and statistical, overlap between all of these concepts (Bardeen et al., 2013, Mansell, 2005, Mansell, 2008). In other words, what different theorists call by different terms may actually refer to the same process, which has been referred to in the social psychology literature as the ‘déjà variable phenomenon’ (Hagger, 2014). This is related to the example of the Blind Men and the Elephant. Just like several blind men feeling different parts of an elephant, insisting they are perceiving something different from one another, each theorist has, to date, an incomplete picture of the one process that they are all studying.

What evidence supports a core process of psychopathology? To begin with, there is convergent evidence from three fields of psychiatry research. First, the symptoms of psychiatric disorders appear to share a great deal of variance. One recent analysis assessed psychiatric symptoms over 38 years in 1007 individuals from the Dunedin birth cohort study (Caspi et al., 2014). They used confirmatory factor analysis to assess the fit of a hierarchical model in which one general psychopathology factor (‘p’) combines with three lower order factors – externalizing, internalizing and thought disorder. They found that the ‘p’ factor correlated with the majority of measures of life impairment more strongly than the specific factors, with the exception of the externalizing factor correlating with certain specific impairments (e.g. suicide attempts, violence convictions). Second, there appears to be a specific brain network that is common to a range of psychiatric disorders as revealed by functional imaging studies (Buckholtz & Meyer-Lindenberg, 2012). Third, there appear to be shared genes that confer risk for a wide range of psychiatric disorders (CDGPGC, 2013, Kendler et al., 2011). In addition, several studies have tested the core psychological process approach directly using different methodologies, measures, analytic methods and samples (Bardeen et al., 2013; Bird, Mansell, Dickens, & Tai, 2013; Hong and Cheung, 2015, McEvoy and Brans, 2013; McEvoy, Mahoney, & Moulds, 2010; Patel, Mansell, & Veale, 2015). In each case, the research questions are the same – can a single factor account for the majority of variance in measures of transdiagnostic processes, or do multiple factors provide a more valid account? A key index of validity is whether the core process is associated with transdiagnostic symptoms – namely anxiety, depression, and in some cases a range of additional diagnostic symptoms.

We identified three studies that concluded that a one-factor model was superior. One study used three measures to identify a core process across experiential avoidance, thought suppression and worry. The study reported a student sample and a community sample of people with chronic physical illnesses (Bird et al., 2013). Structural equation modeling revealed that a single latent factor predicted symptoms of both anxiety and depression at least as well as a three-factor model. The single factor was therefore concluded to be more parsimonious. A meta-analytic study of 73 published articles reported a structural equation model of published effect sizes of the relationship between psychological processes and measures of depression and anxiety. A single factor indicated the best fit (Hong & Cheung, 2015). A third study of two samples – a non-clinical and a mixed clinical sample – used parallel analysis to extract a single factor that emerged from a new scale – the Cognitive Behavioural Processes Questionnaire (CBP-Q). This scale was formed from 15 separate items, each based on a different transdiagnostic process (Patel et al., 2015).

From the above literature, it appears that several studies of differing methodologies converge on a single factor solution. However, there remain a number of limitations. First, the studies to date have either used a limited number of standardized measures or not attempted to analyze the variance at the item level within existing scales. A study is required that collates variance at the item level of detail across a wide range of transdiagnostic measures. We address this limitation in the current study. A second limitation is the clarity of the theoretical mechanism underlying the core process. Essentially, if the core process transcends existing measures, then it is important to sample a wide range of different measures, otherwise the core processes identified may be biased by the initial selection of measures to a restricted domain.

For example, several studies have explored the shared features of transdiagnostic thinking styles. On the one hand, there is evidence in non-clinical and clinical samples that a single factor of recurrent negative thinking (RNT) is correlated with symptoms of multiple different disorders (Mahoney, McEvoy, & Moulds, 2012; McEvoy et al., 2010). Yet further investigation has revealed two qualifications of these findings. First, an additional study of 450 mixed anxious and depressed patients revealed that, in addition to RNT, three further factors – worry, reflection and brooding were extracted and two of these (brooding and worry) independently correlated with symptoms (McEvoy & Brans, 2013). Second, further studies have identified a range of other processes that may mediate the effects of RNT, including intolerance of uncertainty (McEvoy & Mahoney, 2012), metacognitive beliefs, cognitive avoidance and thought control strategies (McEvoy, Moulds, & Mahoney, 2013). Thus, while RNT has been identified as predicting a wide range of symptomology, it is unlikely itself to be the ‘core process’ itself. In a parallel line of work, a ‘core process’ known as distress tolerance has been identified as a higher order factor that unites intolerance of uncertainty, ambiguity, frustration, physical discomfort and negative emotion (Bardeen et al., 2013). Yet, this study did not include any other measures of transdiagnostic processes to clarify whether distress tolerance is the core feature across these processes too.

A related literature that informs the notion of a core process relates to the shared mechanism of change across psychological therapies (Higginson, Mansell, & Wood, 2011; Mansell, 2011). There is an increasing recognition that psychological therapies share mechanisms of change. This has been articulated within conceptual reviews (Mennin, Ellard, Fresco, & Gross, 2013), transdiagnostic treatment models (Barlow, Allen, & Choate, 2004) and within mediation studies of treatment (Goldin et al., 2016; Kocovski, Fleming, Hawley, Ho, & Antony, 2015; Swain, Hancock, Hainsworth, & Bowman, 2015). Taken together, there is an emerging view that the processes of cognitive reappraisal, reduction of emotional and behavioral avoidance, and the development of mindful, or decentered, stances towards experience are fostered across different forms of cognitive behavioral therapies, and potentially across psychotherapies as a whole. These shared mechanisms do not, of course, necessarily converge on a single core process. Yet, there are theoretical perspectives that do make this prediction.

One such example is provided by Hayes and colleagues who have identified the role of experiential avoidance as the key functional property of transdiagnostic processes (Hayes, Wilson, Gifford, Follette, & Strosahl, 1996). Experiential avoidance is defined as being unwilling to remain in contact with particular private experiences (e.g. emotions, thoughts, memories, impulses) and therefore taking steps to alter the form or frequency of these events or the situations that lead to them.

One possible limitation with the notion of experiential avoidance is that it is feasible to avoid private experiences for important, functional reasons. For example, a brain surgeon might need to control their anxiety when conducting an operation; an employee suffering at the hands of a bullying colleague might avoid this person’s company. Therefore, an alternative perspective on a core process is required to explain what differentiates the causes of enduring psychological distress from situational attempts to avoid unpleasant experiences. We turn to perceptual control theory for such an account (PCT; Powers, 1973, Powers, 2008; Powers, Clark, & McFarland, 1960a; Powers, Clark, & McFarland, 1960b). According to PCT, psychological distress is a manifestation of loss of control that emerges during states of chronic conflict between important personal goals. The state of conflict persists because the system governing the conflicting goals is kept outside awareness (for an empirical review, see Kelly, Mansell, & Wood, 2015). When attention is allowed to shift and sustain on this system, changes can occur – through a trial-and-error process known as reorganization – until control is restored. Thus, from the perspective of PCT, any behavior, any thinking style, any strategy, any personal rule and any interpersonal style can be problematic if it is carried out without awareness of, or regard to, the important personal goals with which it might conflict (Mansell, 2005).

The current study tests for the existence of a core process of psychopathology by extracting the common variance across diverse measures of processes known to be associated with psychological distress across disorders, and testing the hypothesis that this core process will be singularly related to symptoms (Mansell, Carey, & Tai, 2015). Specifically, we collected data on cognitive (Repetitive Thinking Questionnaire, RTQ-10, McEvoy, Tribodeau, & Asmundson, 2014), affective (Affect Control Scale, ACS, Williams, Chambless, & Ahrens, 1997), and behavioral (Acceptance Safety behaviors, Escape and Avoidance Scale, AcSEAS, McEvoy, LeBeau, Page, & Craske, in preparation) avoidance. Repetitive negative thinking has been conceptualised as a cognitive strategy for avoiding aversive affective and physical symptoms (Borkovec, Alcaine, & Behar, 2004), the ACS measures fear and behavioral overcontrol of affective symptoms, and AcSEAS Escape/Avoidance subscale assesses escape and wholesale avoidance behaviors due to uncomfortable emotions and symptoms. Consistent with our aim, we expected the shared variance in these constructs to constitute the factor that is associated with symptoms of psychopathology.

In sum, there is a need to develop a parsimonious transdiagnostic model of psychopathology to guide psychological interventions. Therefore, the current study samples a wide range of self-reported processes in a treatment-seeking group of patients with mixed anxiety disorders and depression. We attempted to extract the common variance first using principal components analysis and then compare the validity of the single factor with the validity of later factors that are extracted. We hypothesised that the single factor will have high correlations with symptoms of anxiety and depression, both across the sample as a whole, and within each diagnostic grouping. The current study was not designed to identify the nature of the core process as keeping goal conflict outside awareness, but to complement earlier studies that converge on this account (see Alsawy, Mansell, Carey, McEvoy, & Tai, 2014).