Department of Psychiatry, University of Pennsylvania, Philadelphia, PA, USA.
Department of Mathematics, West Chester University, West Chester, PA, USA.
Psychother Res. 2020 Jan;30(1):53-67. doi: 10.1080/10503307.2018.1544724. Epub 2018 Nov 18.
To introduce readers to instrumental variable analyses for causal inferences using as an example a test of the hypothesis that the quality of the therapeutic alliance has a causal role in relation to the outcome of psychotherapy. We used data from a recent non-inferiority trial of cognitive and dynamic therapies for major depressive disorder in a community mental health setting. The data ( = 161) were analyzed using standard approaches as well as a multilevel 2-stage instrumental variables approach that allows for causal interpretations by removing the influence of unmeasured confounds. Instrumental variables were created at the patient and therapist level using baseline patient and therapist variables. These baseline variables predicted the alliance but were otherwise unrelated to treatment outcome other than through their effects on the alliance. Standard multilevel mixed effects analyses revealed statistically significant associations of the alliance with outcome at the therapist level of analysis. The therapist level effect remained statistically significant when using the instrumental variables approach. Our results support the hypothesis that, at least at the therapist level, the alliance plays a causal role in producing better outcomes. Instrumental variable analyses can be a useful tool to supplement standard analyses.
为了向读者介绍使用实例进行因果推理的工具变量分析，我们检验了治疗联盟的质量是否对心理治疗的结果有因果作用。我们使用了社区心理健康环境中认知和动力治疗重度抑郁症的非劣效性试验中的数据。使用标准方法和多层次 2 阶段工具变量方法对数据（ = 161）进行了分析，该方法通过消除未测量混杂因素的影响，可以进行因果解释。使用基线患者和治疗师变量在患者和治疗师水平上创建了工具变量。这些基线变量预测了联盟，但除了通过它们对联盟的影响之外，与治疗结果没有其他关系。标准多层次混合效应分析显示，联盟与治疗师水平的结果之间存在统计学显著关联。当使用工具变量方法时，治疗师水平的效果仍然具有统计学意义。我们的结果支持这样的假设，即至少在治疗师水平上，联盟在产生更好的结果方面起着因果作用。工具变量分析可以是补充标准分析的有用工具。
