All types of mental illness are associated with premature mortality (Plana-Ripoll et al., 2019), especially with cancer and cardiovascular disease (Joukamaa et al., 2001). Further, an estimated 14.3% of overall global mortality may be attributed to mental health problems (Walker et al., 2015). In 2016, in the European Union, about 84 million people reported having a mental health problem, i.e., one in six people. The most frequent mental illnesses are anxiety and depression, affecting 5.4% and 4.5% of the population, respectively (OECD/EU, 2018).

Psychological distress, though not a mental health diagnosis, depicts symptoms of anxiety and depression, and can become a long-lasting and disabling disorder. There is ample published evidence associating psychological distress to an increased risk of mortality in general (Huppert and Whittington, 1995; Puustinen et al., 2011; Robinson et al., 2004; Yang et al., 2020), cancer- (Batty et al., 2017) and cardiovascular disease-related mortality in particular (Batty et al., 2016; Lee and Singh, 2020; Yang et al., 2020).

The importance of screening for early detection of mental health problems is widely recognize. Yet, much remains to learn about the mechanisms through which a prior mental illness diagnosis, either controlled with medication or not, may influence the association between psychological distress and mortality. In this study we chose the General Health Questionnaire (GHQ) (Goldberg et al., 1997), a widely used screening instrument to measure psychological distress, especially its 12-item version. The GHQ was originally designed as a screening tool for use in both clinical and community settings to detect cases of psychiatric morbidity or psychological distress in the population.

The aim of this study is to evaluate the association between psychological distress and all-cause-, cardiovascular disease-, and tumor-related mortality, according to whether the patient had a previous mental disorder diagnosis and whether the participant was taking a prescription drug for a mental health issue.