en Psychiatry Psychiatry Original Research Original Research <span style="font-size:13pt"><span style="text-justify:kashida"><span style="text-kashida:0%"><span style="text-autospace:none"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="font-style:italic"><b>&nbsp;&nbsp;</b><b><span style="font-size:9.0pt"><span style="font-style:normal">&nbsp; Background: </span></span></b><span style="font-size:9.0pt"><span style="font-style:normal">Fatigue refers to a lack of energy that makes it challenging to initiate or maintain voluntary activities. The Chalder Fatigue Scale (CFS) is a tool designed to assess the severity of fatigue. Studies indicate that it has strong validity and internal reliability, measuring both the mental and physical aspects of fatigue. We aimed to translate this questionnaire and to evaluate its psychometric properties in Iran.</span></span></span></span></span></span></span></span><br> <span style="font-size:13pt"><span style="text-justify:kashida"><span style="text-kashida:0%"><span style="text-autospace:none"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="font-style:italic">&nbsp;&nbsp; <b><span style="font-size:9.0pt"><span style="font-style:normal">Methods: </span></span></b><span style="font-size:9.0pt"><span style="font-style:normal">The translation process adhered to guidelines for cross-cultural adaptation of self-report measures. This cross-sectional study included 70 participants. The reliability of the CFS was evaluated through internal consistency and test&ndash;retest reliability. To determine test&ndash;retest reliability, each participant completed the scale twice, with a two-week interval between assessments. Construct validity was assessed using factor analysis and principal component analysis. For content validity, a form was completed by 15 experts to evaluate the relevance and necessity of the items, calculating both the Content Validity Index (CVI) and the Content Validity Ratio (CVR).</span></span></span></span></span></span></span></span><br> <span style="font-size:13pt"><span style="text-justify:kashida"><span style="text-kashida:0%"><span style="text-autospace:none"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="font-style:italic"><span style="font-size:9.0pt"><span style="font-style:normal">&nbsp;&nbsp; <b>Results:</b> The average age of the participants was 38 years, with a standard deviation of 8.52. Among the participants, 22 (31.4%) were male. Content validity analysis yielded a CVI of 0.88, indicating acceptable relevance, and a CVR of 0.81, demonstrating good content validity. Factor analysis identified a two-factor solution. The Cronbach&rsquo;s alpha coefficient for the CFS was 0.89. The Intraclass &nbsp;&nbsp;Correlation Coefficient for the CFS was 0.79 (95% confidence interval: 0.66&ndash;0.87, </span></span><span style="font-size:9.0pt">P</span><span style="font-size:9.0pt"><span style="font-style:normal"> < 0.001), reflecting good test-retest reliability.</span></span></span></span></span></span></span></span><br> <span style="font-size:13pt"><span style="text-justify:kashida"><span style="text-kashida:0%"><span style="text-autospace:none"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="font-style:italic"><span style="font-size:9.0pt"><span style="font-style:normal">&nbsp;&nbsp; <b>Conclusion:</b> The results indicate that the CFS is a reliable and valid tool for assessing fatigue, making it suitable for use in both research and clinical environments in Iran.</span></span></span></span></span></span></span></span><br> &nbsp; Fatigue, Validity, Reliability, Persian, Chalder Fatigue Scale 64 68 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-9318-1&slc_lang=en&sid=1 Zahra Banafsheh Alemohammad zahra_5721@yahoo.com 200319475328460096303 200319475328460096303 No Occupational Sleep Research Center, Baharloo Hospital, Tehran University of Medical Sciences, Tehran, Iran Samaneh Akbarpour akbarpour691@gmail.com 200319475328460096304 200319475328460096304 No Occupational Sleep Research Center, Baharloo Hospital, Tehran University of Medical Sciences, Tehran, Iran Khosro Sadeghniiat-Haghighi sadeghniiat@yahoo.com 200319475328460096305 200319475328460096305 No Occupational Sleep Research Center, Baharloo Hospital, Tehran University of Medical Sciences, Tehran, Iran Ahmad Khajeh-Mehrizi khmehrizi.a@gmail.com 200319475328460096306 200319475328460096306 No Department of Hematology and Medical Oncology, Imam Khomeini Hospital Complex, Institute of Cancer, Tehran University of Medical Sciences, Tehran, Iran Laya Golshani layagolshani@yahoo.com 200319475328460096307 200319475328460096307 No Occupational Sleep Research Center, Baharloo Hospital, Tehran University of Medical Sciences, Tehran, Iran Ania Rahimi-Golkhandan aniarahimi.g@gmail.com 200319475328460096308 200319475328460096308 Yes Occupational Sleep Research Center, Baharloo Hospital, Tehran University of Medical Sciences, Tehran, Iran