Most clinicians view depression as a painful disorder in which motivation to pursue adaptive goals is lacking and cognition is impaired. An alternative hypothesis—grounded in a common evolutionary approach—suggests that depression is inherently motivational and evolved to motivate avoidant learning of harmful situations. Testing these hypotheses requires a clear definition of “disorder”. Wakefield’s harmful dysfunction evolution-based definition proposes that all unambiguous cases of disorder involve a malfunctioning adaptation. These hypotheses—functional adaptation and malfunctioning adaptation—are mutually exclusive and require a common research strategy. One must identify and map out the relevant adaptation—characterized by a high degree of non-random organization and coordination for promoting a function—which will eventually result in a conceptual blueprint of where and how the adaptation can malfunction. Using inescapable shock in rats and physicians’ emotional responses to medical errors to provide context, we show how the symptoms of melancholic depression exhibit signs of adaptation for motivating a time-consuming, attentionally-demanding, energetically-expensive avoidant learning style after experiencing a harmful event. We discuss how this adaptationist approach may provide insight into spontaneous remission and the effects of psychotherapies and antidepressant medications.

大多数临床医生将抑郁症视为一种痛苦的疾病，其中缺乏追求适应性目标的动力并且认知能力受损。另一种假设——基于一种常见的进化方法——表明抑郁症本质上是动机性的，并且进化为激发对有害情况的回避学习。检验这些假设需要对“障碍”有明确的定义。韦克菲尔德的有害功能障碍基于进化的定义提出，所有明确的障碍病例都涉及适应障碍。这些假设——功能性适应和故障适应——是相互排斥的，需要一个共同的研究策略。人们必须确定并绘制相关的适应——其特征是高度的非随机组织和协调以促进一项功能——这最终将产生一个关于适应性在哪里以及如何发生故障的概念蓝图。使用大鼠不可避免的休克和医生对医疗错误的情绪反应来提供背景，我们展示了忧郁抑郁症的症状如何表现出适应迹象，以在经历有害的经历后激发耗时、需要注意力、精力充沛的回避学习风格事件。