Associations between diseases of the mouth and mental disorders: A scoping review of longitudinal studies.

BACKGROUND: Mental disorders and oral health conditions frequently co-occur. We mapped and critically reviewed the literature on longitudinal associations between oral health conditions and mental disorders. METHOD: MEDLINE, Embase and PsycInfo were searched for longitudinal studies published during the last 25 years. Two reviewers independently screened, reviewed full-text and extracted data before synthesizing the evidence. Associations between oral and mental disorders were illustrated as Sankey diagrams. The review protocol was pre-registered (https://osf.io/vrpu9). FINDINGS: From 165 included studies, we identified 118 studies investigating 35 independent associations between 16 oral exposures and 12 mental disorder outcomes. Another 42 studies investigated 32 associations between 17 mental disorder exposures and 14 oral outcomes. Five studies reported bidirectional associations. Most reports linked tooth loss to Alzheimer's disease/other dementias (18 studies) and cognitive impairment (15 studies), with periodontitis linked to Alzheimer's disease/other dementias (16 studies). Conversely, depression (10 studies), dementia (6 studies) and sleep disorder (5 studies) were attributed to temporomandibular disorders (TMD; 10 studies), periodontitis (8 studies) and caries (7 studies) outcomes. Depressive and anxiety disorders were linked bidirectionally with TMD and eating disorders. INTERPRETATION: Prevention and early management of oral and mental disorders may mitigate their reciprocal risk, thereby lowering the overall disease burden.