The　association　between　constipation　and　suicidal　ideation　remains　inadequately　explored.　This　study　aims　to　investigate　the　potential　correlation　between　constipation　and　suicidal　ideation　in　US　adults,　while　assessing　the　mediating　role　of　depression.For　this　cross-sectional　study,　a　total　of　13,493　adults　aged　20　years　and　older　were　included　from　the　National　Health　and　Nutrition　Examination　Survey　2005–2010.　The　definition　of　constipation　was　defined　by　considering　the　consistency　or　frequency　of　stool.　The　ninth　item　on　the　Patient　Health　Questionnaire-9　(PHQ-9)　evaluated　suicidal　ideation,　and　depression　was　evaluated　using　the　PHQ-8　score.　Adjusted　odds　ratios　(ORs)　were　calculated　using　multivariate　logistic　regression　models.　Sensitivity　analysis　was　performed　to　ensure　stable　results.　Furthermore,　study　employed　mediation　analysis　to　examine　the　effect　of　constipation　on　suicidal　ideation　through　depression.　The　bootstrapping　method　was　used　to　assess　the　significance　of　the　mediation　effect.　After　controlling　for　demographic　factors,　risk　behaviors,　comorbidities,　dietary　intake,　and　relevant　medications,　constipation　was　associated　with　an　increased　risk　of　suicidal　ideation　(OR　1.41,　95%CI　1.08–1.83,　P　=　0.011).　Sensitivity　analyses　showed　the　stability　of　the　results.　Moreover,　mediation　analysis　demonstrated　a　significant　direct　effect　of　constipation　on　suicidal　ideation　(P　=　0.016),　with　depression　playing　a　partial　mediating　role　in　this　interaction　(40.81%,　P　＜　0.0001).　In　conclusion,　this　study　demonstrated　a　significant　association　between　constipation　and　suicidal　ideation,　with　depression　serving　as　a　partial　mediator　in　this　relationship.　Further　prospective　longitudinal　studies　are　essential　to　establish　a　definitive　causal　relationship　between　these　factors　so　as　to　guide　the　development　and　implementation　of　targeted　intervention　strategies.　©　The　Author(s)　2025.