BackgroundPrevious studies have identified a close relationship among psychological neglect and abuse， negative affect， different stages of adolescence， and suicidal ideation. However， the mechanisms underlying the impact of psychological abuse and neglect on suicidal ideation among left-behind adolescents remain unclear， and this field of research is still in its relative infancy. ObjectiveTo explore the relationship between psychological neglect/abuse and suicidal ideation among left-behind adolescents， as well as the mediating role of negative affect and the moderating effect of different stages of adolescence， so as to provide insights for preventing and intervening suicidal ideation in this population. MethodsFrom November 2021 to May 2022， a cluster random sampling technique was utilized to select 2 309 left-behind adolescents in western China. Assessments were conducted using the Child Psychological Abuse and Neglect Scale （CPANS）， the Positive and Negative Suicide Ideation （PANSI） and the Positive and Negative Affect Schedule for Children （PANAS-C）. Spearman correlation coefficients were calculated across all samples， and Process 4.1 was employed to test the mediating role of negative affect and the moderating role of different stages of adolescence in the pathway linking psychological abuse/neglect to suicidal ideation. ResultsA total of 2 119 left-behind adolescents （mean age： 14.94±1.20 years） completed the study， with males comprising 51.34% （1 088/2 119） and females 48.66% （1 031/2 119）.Among left-behind adolescents， scores on CPANS psychological neglect subscale showed positive correlations with both psychological abuse subscale scores and PANAS-C negative affect subscale scores （r=0.446， 0.496， P<0.01）. Additionally， CPANS psychological neglect and psychological abuse subscale scores were also positively correlated with PANSI scores （r=0.487， 0.508， P<0.01）. Furthermore， PANAS-C negative affect subscale scores demonstrated a positive correlation with PANSI scores （r=0.499， P<0.01）. Negative affect partially mediated the relationship between psychological abuse/psychological neglect and suicidal ideation， with effect sizes of 0.166 （95% CI： 0.141~0.191） and 0.131 （95% CI： 0.112~0.152）. Different stages of adolescence moderated the latter part （negative emotion → suicidal ideation） of the indirect mediation path from psychological neglect to suicidal ideation through negative affect （β=-0.066， P<0.01）. ConclusionBoth psychological neglect and psychological abuse may influence suicidal ideation among left-behind adolescents via negative affect. Moreover， different stages of adolescence may moderate the indirect path from psychological neglect to suicide ideation through negative affect.