我國臨床心理實務及精神鑑定於智能不足個案出現診斷蔭蔽現象之探討

Abstract

診斷蔭蔽（Diagnostic overshadowing）係指實務工作者評估臨床展現較複雜的個案時，因過於注重特定疾病症狀而忽視其餘臨床資訊，並低估其他疾病存在之可能性，導致評估判斷上未能如實反映個案狀態，形成診斷偏誤。過往針對智能不足個案的診斷蔭蔽研究多是以思覺失調症為個案臨床描述，但因受限於發展上的困難，智能不足群體相較於典型發展群體而言更容易經歷負面生活事件（Wigham & Emerson, 2015），並在後續產生創傷相關的心理困擾（Hove et al., 2016; Wigham et al., 2014），是故以創傷後壓力症為臨床描述探討診斷蔭蔽的現象實屬重要；此外，部分重大創傷事件會進入司法程序，使得臨床心理師於精神鑑定中也可能接觸此群體，因此亦需釐清診斷蔭蔽如何受精神鑑定之脈絡影響。本研究以兩個參與者內設計的實驗來回應上述兩議題，透過呈現不同臨床描述，檢驗我國臨床心理師是否受診斷蔭蔽偏誤影響。研究結果發現參與者面對智能不足個案時，考量多重診斷的比例明顯高於單一診斷，但其判斷涵蓋研究預設之共病診斷的比例顯著低於中等智能個案情境，顯現出智能不足個案於共病上的判斷困難，結果上相對不支持診斷蔭蔽現象；然而，參與者評分智能不足個案具有其他心理疾病的可能性較中等智能個案來得低，且此現象在精神鑑定的脈絡下僅出現於被害人的個案情境，顯示診斷蔭蔽現象存在於司法情境的脈絡下，且會受到個案身份別的不同而有所差異，此結果可提供給接觸智能不足個案的臨床心理師作為往後實務工作之提醒。

Diagnostic overshadowing refers to a bias in clinical judgment when clinicians focus only on a particular condition while over-looking other possible symptoms or psychopathology in cases of comorbidity. Previous research on the diagnostic overshadowing of intellectual disability have predominantly focused on cases of schizophrenia or have mainly used schizophrenia-based case descriptions. Due to deficits in developmental abilities, persons with intellectual disability have been found to be more likely to experience negative life events than the general population (Wigham & Emerson, 2015) and develop trauma-related mental disorders later (Hove et al., 2016; Wigham et al., 2014). However, it is unclear whether diagnostic overshadowing can be observed while comorbid with posttraumatic stress disorder (PTSD). In addition, clinical psychologists are often requested to assess a person’s mental state in the legal context when severe traumatic events are involved; therefore, it is important to explore the influence of forensic contextual factors on diagnostic overshadowing. The current study used two experiments with within-participant design to investigate the above-mentioned issues. By providing different clinical case descriptions, this study aimed to examine whether clinical judgements made by clinical psychologists in Taiwan are influenced by diagnostic overshadowing. We found that clinical psychologists preferred multiple diagnoses than single diagnosis when facing intellectually disabled clients, but the diagnostic impression of trauma- and stressor-related disorders was less likely to be given than in the typical developmental scenario, and the participants also rated a lower likelihood of comorbidity in cases with intellectual disability. Furthermore, in the psychiatric assessment context, this effect was only found when clients were identified as victims. The results of this study show that the diagnostic overshadowing phenomenon in cases with intellectual disability can be found in the forensic contexts. These findings about diagnostic overshadowing deserve more attention and can provide practical recommendations for clinical psychologists especially working with cases of intellectual disability.