People with an Intellectual Disability (ID) are around 4 times more likely to suffer with a mental health disorder than IQ-typical people, however previous studies have shown they may be less likely to be diagnosed. One suggested cause of this is the diagnostic overshadowing bias: the tendency for practitioners to attribute unusual behaviour, thoughts or feelings to a person’s ID and not a separate mental health disorder.

In the current study N = 87 participants were randomly assigned 1 of 2 clinical vignettes describing a client who is displaying symptoms of mental health disorder. Vignette 1 described a client with an IQ of 105 who graduated from high school. Vignette 2 described a client with an IQ of 55 who attended special classes throughout school. All other details were identical. Participants then rated the likelihood of 7 diagnoses on a 5-point Likert scale.

Contrary to our hypothesis participants were not less likely to diagnose a mental health disorder in people with an ID and this was found to exist across all profession types involved in the study.

Although these findings indicate that the diagnostic overshadowing bias may not be present in Australia, several factors including a reported lack of confidence in working with clients with an ID suggest the inclusion of ID specific training may be beneficial.

智障人士患精神健康障碍的可能性是智商一般人群的4倍左右，但是先前的研究表明，他们被诊断出的可能性较小。一个可能的原因是诊断上的阴影偏见：从业者倾向于将异常的行为，思想或感觉归因于一个人的ID，而不是一个单独的心理健康障碍。

在本研究中，将N = 87名参与者随机分配给2个临床小插曲中的1个，这些小插曲描述了一位出现精神健康障碍症状的服务对象。Vignette 1描述了一位智商为105的客户，他的高中毕业。Vignette 2描述了一个智商为55的客户，他在整个学校都参加过特殊课程。所有其他细节相同。然后，参与者以5分李克特量表对7次诊断的可能性进行评估。

与我们的假设相反，参加者在具有ID的人中诊断出精神健康障碍的可能性也不低，并且发现这种情况存在于研究涉及的所有专业类型中。

尽管这些发现表明澳大利亚可能不存在诊断上的偏见偏见，但一些因素（包括据报道缺乏与带有ID的客户合作的信心）表明，包括ID特定培训可能是有益的。