[Abstract]
Background: Methadone maintenance treatment (MMT) is effective in decreasing opioid use or facilitating abstinence. Previous studies using small opioid use disorder samples suggest that cognitive impairments including impulsivity and executive functions may partially improve on MMT, but a range of deficits may persist. However, systematic assessments with larger samples are needed to confirm the profile of cognitive functions on MMT.
Methods: We assessed four types of impulsivity (delay discounting, reflection impulsivity, risk taking and motoric impulsivity), executive functioning (spatial working memory, paired associative learning and strategic planning) and drug cue-induced craving in a relatively large population (115 MMT patients, 115 healthy controls). The relationships between impulsivity, drug cue-induced craving and addiction-related variables were also assessed.
Results: Delay discounting, as well as drug cue-induced craving was increased in patients, while motoric impulsivity was lower than in controls. Paired associative learning was additionally impaired, which was explained by increased depression and anxiety levels in patients. Within the MMT group, the delay discounting and drug-cue induced craving scores were positively correlated with self-reported urgency, but unrelated to methadone dosage, duration on methadone, withdrawal symptoms, or presence of nicotine dependence.
Conclusions: Our findings highlight increased delay discounting and cue-induced craving in MMT patients suggesting a potential role for trait effects in delay discounting. Although previous smaller studies have shown impaired executive function, in our large sample size on chronic MMT we only observed impaired associative learning related to depressive and anxiety symptoms highlighting a role for managing comorbid symptoms to further optimize cognitive function.
【中文摘要】
背景：美沙酮藥物維持治療能夠有效降低非法阿片類藥物的使用，或能夠促進戒斷。前人的小樣本研究提示美沙酮替代治療能夠部分緩解阿片類藥物成癮患者的高衝動和認知功能異常，但還有一部分缺陷仍然存在。然而，研究結論還需要大樣本研究加以驗證。
方法：本研究系統地測量了美沙酮維持治療患者四種不同類型的衝動性（延遲折扣、思考缺乏、風險偏好、運動抑制）、三種執行功能（空間工作記憶、配對聯繫學習、策略計劃），以及由藥物圖片誘發的藥物渴求情況。研究納入了115名美沙酮藥物維持治療患者，以及115名健康人作為對照。除了組間比較以外，本研究也對衝動、藥物渴求、與成癮相關的變量之間的相關性做了分析。
結果：患者表現出較高的延遲折扣率，以及較高的藥物線索誘發的藥物渴求，而患者在運動抑制方面的衝動性低於健康人。患者在配對聯繫學習任務中表現出缺陷，但該任務指標異常可通過患者的抑鬱和焦慮水平進行解釋。患者的延遲折扣率、高藥物渴求與他們的衝動性量表得分（迫切度評分）正相關，但與美沙酮用量、接受治療時長、戒斷症狀評分、尼古丁依賴程度沒有顯著相關性。
結論：我們的研究結果顯示，美沙酮藥物維持治療患者在延遲折扣和線索誘發的藥物渴求上存在異常，且與患者的衝動性特質有關。儘管前人的研究發現美沙酮治療患者的高級認知功能存在異常，我們的大樣本研究提示長期接受治療患者僅在配對聯繫學習任務中存在缺陷，且該指標與患者的抑鬱和焦慮情緒有關，提示也許能夠通過改善患者的共病症狀進一步改善患者的高級認知功能。