Psychological treatments for early psychosis can be beneficial or harmful, depending on the therapeutic alliance: an instrumental variable analysis

Abstract

Background: The quality of the therapeutic alliance (TA) has been invoked to explain the equal effectiveness of different psychotherapies, but prior research is correlational, and does not address the possibility that individuals who form good alliances may have good outcomes without therapy.

Method: We evaluated the causal effect of TA using instrumental variable (structural equation) modelling on data from a three-arm, randomized controlled trial of 308 people in an acute first or second episode of a non-affective psychosis. The trial compared cognitive behavioural therapy (CBT) over 6 weeks plus routine care (RC) v. supportive counselling (SC) plus RC v. RC alone. We examined the effect of TA, as measured by the client-rated CALPAS, on the primary trial 18-month outcome of symptom severity (PANSS), which was assessed blind to treatment allocation.

Results: Both adjunctive CBT and SC improved 18-month outcomes, compared to RC. We showed that, for both psychological treatments, improving TA improves symptomatic outcome. With a good TA, attending more sessions causes a significantly better outcome on PANSS total score [effect size -2.91, 95% confidence interval (CI) -0.90 to -4.91]. With a poor TA, attending more sessions is detrimental (effect size +7.74, 95% CI +1.03 to +14.45).

Conclusions: This is the first ever demonstration that TA has a causal effect on symptomatic outcome of a psychological treatment, and that poor TA is actively detrimental. These effects may extend to other therapeutic modalities and disorders.

Keywords: Cognitive therapy; counselling; first episode; psychosis; therapeutic alliance.

Fig. 1.

X₁, X₂ and X₃ are baseline variables: the baseline Positive and Negative Syndrome Scale (PANSS) total score, years of education and log of the duration of untreated psychosis. C₁ and C₂ are different centres. The bottom row includes randomization, Z (coded in binary) and the interaction of randomization and the baseline variables. Outcome, Y is the 18-month PANSS total score. S is sessions and SA is the interaction of sessions and alliance. Measurement errors are labelled ε₁, ε₂ and ε₃. The bottom row therefore shows the interaction of randomization and variables having a causal effect on the number of sessions attended and the interaction of sessions and alliance (the effect of alliance is modelled in a dose-response manner). In turn, these post-randomization variables have a causal effect on the symptomatic outcome (the PANSS 18-month outcome score). The paths connecting the post-randomization variables to outcome are of primary interest and these are shown in the results section as β_S and β_SA. The top row of Fig. 1 shows the baseline variables directly affecting the PANSS 18-month score. The strength of these causal relationships is the same for patients randomized to receive a psychological therapy or not. By using the interactions of randomization and baseline variables in the bottom row, and coding randomization to treatment as usual only as 0, patients not receiving a talking therapy are not included in the causal pathway estimates in the bottom part of the diagram.