Mental-physical multimorbidity is highly prevalent and challenges the conventional thinking of the single disease paradigm in healthcare systems. Mental and physical health are closely related in a bidirectional manner. Persons with mental-physical multimorbidity experience a heavy symptom and treatment burden in addition to a lower quality of life and an impaired medical prognosis. Healthcare is complicated by symptom overlap, poor communication and uncoordinated care. New cross-sectional and patient-centred approaches are necessary to counter the adversities of mental-physical multimorbidity.