The triangulation of multimorbidity: A systematic review of primary sleep disorders, hypertension, and psychiatric disorders.

Despite the growing evidence of the interconnectedness of hypertension, sleep disorders, and mental health, the exact nature of the relationships and the potential for combined or synergistic effects remain unclear. Potential mechanisms include environmental factors, family stressors, financial difficulties, treatment side effects and shared pathophysiological comorbidities. Therefore, this systematic review aimed to address this gap by assessing comprehensively the interrelationships between these three conditions among adults. A systematic review was conducted in line with the preferred reporting items for systematic reviews and meta-analyses. The literature search was performed across three databases: PubMed, SCOPUS, and CINAHL. From an initial pool of 1759 articles, 45 met the inclusion criteria and were used in the analysis. Most studies assessed the associations between the three conditions pairwise, using different definitions and methods. Positive (60-75%) or non-significant associations (25-40%) were commonly reported, with no inverse associations identified. This consistent pattern suggests that these conditions are interrelated, even when statistical significance was not reached in some cases. In conclusion, the association between sleep disorders, hypertension, and psychiatric diseases is highlighted in the majority of studies, showing predominantly positive or non-significant relationships, with no studies reporting inverse associations among these three conditions. These findings suggest that addressing these conditions in an integrated manner may improve clinical management and patient outcomes.