Should psychosocial treatment for schizophrenia focus on the proximal or distal consequences of the disorder?

Schizophrenia is characterized by a range of symptoms, most notably psychotic and negative symptoms, with mood and substance abuse problems also common. Although the disorder is diagnosed mainly in terms of symptoms, impairments in psychosocial functioning are another defining feature, including the ability to work or go to school, social relationships and the capacity for independent living. While a decline in cognitive functioning is not incorporated into most diagnostic criteria for schizophrenia, it is a common correlate widely believed to occur in most people with the disorder. The broad and pervasive impact of schizophrenia, combined with the relatively early age at which the disorder usually develops, in early adulthood, is a major reason for it being ranked as one of the 10 most burdensome diseases in the world, despite its prevalence of only about 1% in the general population (Murray & Lopez, 1996).

Considering the impact of schizophrenia on the wide range of domains of functioning, the question is often posed as to which affected areas should psychosocial treatments focus on? Should treatment address symptoms and associated types of impairments or broader functional outcomes or both? Are there any organizing principles that could guide clinicians in selecting which outcomes should be targeted by psychosocial interventions? In this commentary, I propose that the distinction between proximal–distal effects of a disease provides a theoretical basis for focusing treatment on the broader impact of schizophrenia on functional outcomes, and gives clinicians a useful heuristic for planning and evaluating their psychosocial treatment efforts.

The proximal–distal concepts

The concept of proximal–distal influences has been used to distinguish the most immediate or direct effects of a disease or an intervention from the longer term and more indirect effects (Brenner et al., 1995; Ryan, 2009). By definition, the more proximal or immediate the effect, a disease has on a specified outcome, the stronger the impact of the disease and the weaker the effect of other, non-disease factors on that outcome. Conversely, the more distal or long-term the effect of a disease on an outcome, the weaker the impact of the disease and the stronger effect of non-disease factors (e.g. the environmental and psychological processes) on that outcome.

In schizophrenia, the most immediate consequences of the illness are assumed to be signs of psychopathology and cognitive impairment. Schizophrenia has long been hypothesized to be a neurodevelopmental disorder (Weinberger & Marenco, 2003), with impaired cognitive functioning increasing the risk for developing it (Khandaker et al., 2011) and a decline in cognitive performance presaging the onset of symptoms (van Oel et al., 2002). Depression and negative symptoms are among the first symptoms that occur, on average appearing several years before the onset of psychotic symptoms in schizophrenia (Häfner et al., 1999). Drug and alcohol abuse is also one of the earliest psychopathological manifestations of schizophrenia, with upwards of 50% of individuals with a first episode of psychosis already having problematic substance use (Archie & Gyömörey, 2009). While psychotic symptoms typically develop after mood problems and negative symptoms, they are central to the diagnosis of schizophrenia. The fact that antipsychotic medications have such a profound effect on psychotic symptoms suggests that they modify basic brain or neurotransmitter processes related to more proximal, biological causes of the disorder. Thus, the characteristic psychopathology and cognitive impairment associated with schizophrenia can be conceptualized as the most proximal clinical consequences of the disorder.

The longer term consequences of schizophrenia, on the other hand, are generally assumed to be the profound psychosocial impairment associated with the illness that is responsible for its significant burden throughout the world: reduce role functioning and capacity for self-care and independent living. It is well established that impaired cognitive functioning and symptoms are major contributing factors to poor psychosocial functioning in schizophrenia (McGurk & Mueser, 2004; Pogue-Geile, 1989; Racenstein, et al., 2002). However, cognitive impairment and symptoms do not account for all the variance in different dimensions of impaired psychosocial functioning, and they are even less predictive of functioning over the long-term (Addington et al., 2003; Carpenter & Strauss, 1991; Suslow et al., 2000). The weak association between cognitive impairment and symptoms, and community and interpersonal functioning, reflects the distal nature of psychosocial functioning, which can be influenced by a wide variety of factors other than those directly related to the illness. For example, someone with strong social supports, such as from family members or mental health professionals, may be more able to sustain independent living in the community despite severe symptoms or cognitive impairments that would preclude such independence in another person with similar challenges but less social support.

Aside from the effects of social and other environmental supports and resources on functioning (Rapp & Goscha, 2006), broader system and societal factors can also influence psychosocial functioning despite the effects of illness-related factors, such as laws protecting the rights of people with a mental illness (EEOC, 1997), policies promoting social inclusion (Boardman et al., 2010), and social and role opportunities. In addition, individual person-related factors may affect psychosocial functioning in spite of the symptoms and cognitive challenges. For example, the personal agency of the client is central to the concept of recovery (Roe & Davidson, 2008), and is reflected by qualities such as self-determination, self-esteem, self-efficacy and hope, which can contribute to better psychological and overall functioning (Hasson-Ohayon et al., 2009; Ryan & Deci, 2000). Personal skills, such as social and self-care skills, can likewise optimize functioning in schizophrenia in spite of the symptoms and cognitive impairments (Bellack et al., 1990; Harvey et al., 2007).

Implications for treatment

At the present, the pathophysiological basis of schizophrenia is unknown. This inherently limits the ability to design potent psychosocial treatments that address the most proximal clinical effects of schizophrenia, although interventions can target non-illness-related factors that affect symptoms and cognitive impairment, or moderate their effects on functioning. In contrast, a greater variety of non-illness related factors are known to impact on the more distal effects of schizophrenia on psychosocial functioning, suggesting there are more opportunities to influence these outcomes. The implications are that psychosocial treatments for schizophrenia have greater potential for improving the distal than proximal consequences of the illness, and therefore priority should be placed on focusing treatment on improving functional outcomes over ameliorating symptoms and cognitive impairments.

Figure 1 illustrates the psychosocial treatment implications of the distinction between the proximal and distal effects of schizophrenia. The most proximal clinical effects of schizophrenia on symptoms and cognitive functioning influence the more distal outcomes of psychosocial functioning. Potentially changeable moderating factors, including the individual's personal agency and skills, as well as supports and resources, and the health system and society, are hypothesized to have a major effect on the distal outcomes (depicted by thick arrows), while these factors can also have a weaker effect on the proximal outcomes (depicted by thin arrows). Examples of psychosocial interventions that address moderating factors of distal outcomes include enhancing personal skills through social skills training in order to improve social functioning and independent living (Kurtz & Mueser, 2008), and increasing environmental supports through supported employment in order to improve work outcomes (Drake et al., 2012). Other potentially beneficial approaches to improving distal outcomes by altering moderating factors can be inferred from the figure, such as strategies for increasing the individual's sense of personal agency.

Figure 1.  Treatment implications based on the distinction between proximal vs. distal effects of schizophrenia. The proximal effects are the most immediate consequences of the illness in areas such as symptoms and cognitive impairment, whereas the distal effects are the longer term consequences on areas such as role functioning and independent living. Changeable moderating factors at the level of the person, the environment and society have a stronger influence on distal outcomes than proximal outcomes. Therefore, psychosocial treatment should focus primarily on targeting the distal, functional outcomes of schizophrenia, and focus on the proximal, symptomatic and cognitive outcomes only when they clearly interfere with efforts to improve functioning.

Psychosocial interventions can also target moderating factors that have an impact on the proximal outcomes of schizophrenia, although the effects of these interventions are hypothesized to be more modest than interventions addressing distal outcomes. For example, cognitive-behavioral therapy for psychosis may reduce the severity of psychotic symptoms through a combination of increasing personal agency by normalizing psychotic symptoms (reducing low self-esteem) and promoting hope and self-efficacy, and teaching more effective personal skills for coping with persistent symptoms, and examining and changing inaccurate or unhelpful distressing thoughts and beliefs related to symptoms (Wykes et al., 2008). Another example is cognitive remediation, which may reduce cognitive impairment or its effects on functional outcomes by enhancing personal skills through a combination of practicing cognitive exercises, and learning more effective strategies for solving cognitive challenges or compensating for the effects of cognitive difficulties on psychosocial functioning (Wykes et al., 2011). In the figure, in addition to arrows emanating from the moderating factors to the proximal outcomes, there are two arrows from the proximal outcomes to the personal agency and personal skill moderating factors, reflecting the fact that the symptoms and cognitive impairment schizophrenia of schizophrenia do have an impact on compromising these factors, which can nevertheless be changed through psychosocial treatment.

While psychosocial interventions may have a greater potential impact on the distal outcomes of schizophrenia compared with proximal outcomes, this does not mean that treatment should only focus on improving functioning. Symptoms and cognitive impairments do interfere with psychosocial functioning, and can reduce benefit from treatments targeting functional outcomes (McGurk & Mueser, 2004; Mueser et al., 1992; Wykes & Dunn, 1992). However, the proximal–distal concept suggests that symptoms and cognitive functioning should not be a primary focus for treatment. Rather, these proximal outcomes should be addressed in the context of efforts to improve specific functional outcomes as the primary goal, especially when there is evidence that symptoms or cognitive functioning pose an obstacle to more direct treatment efforts targeting these distal outcomes (e.g. social skills training, supported employment). This suggestion is supported by research showing that cognitive remediation can enhance the benefits of other psychosocial treatments on functional outcomes in clients with cognitive impairment, but has negligible effects on functional outcomes when provided as a stand-alone intervention (Wykes et al., 2011).

The proposed framework suggests that a primary focus of treatment on the distal functional outcomes of schizophrenia is more likely to be productive than on the proximal outcomes of symptoms and cognitive impairment. In addition to the broader range of opportunities for improving functioning in schizophrenia, a focus on psychosocial outcomes may also be more in tune with the preferences of clients, who frequently express a strong desire to address needs in areas such as work, housing and social relationships (Ralph & Corrigan, 2005; Rogers et al., 1991). Finally, client motivation to address illness-related problems, such as severe symptoms and relapses, can often be most effectively harnessed through a collaboration focused on the attainment of functional goals, and that includes the exploration of how aspects of the psychiatric disorder may interfere with progress towards those goals.

Acknowledgements

I appreciate feedback provided by Marianne D. Farkas and Sally Rogers on an earlier draft of this paper.