Thornicroft and colleagues recently reported on the undertreatment of people with major depressive disorder (MDD) in 21 countries. ^{Reference Thornicroft, Chatterji, Evans-Lacko, Gruber, Sampson and Aguilar-Gaxiola1} Their conclusions suggest that better diagnosis and treatment of major depression worldwide, particularly in low-income countries, should improve health outcomes. Such improvements should contribute, in particular, to reducing rates of suicide, which are closely associated with MDD. ^{Reference Tondo and Baldessarini2}

Accordingly, we considered relationships between the reported national rates of treatment for MDD overall or for identified cases who wanted treatment, ^{Reference Thornicroft, Chatterji, Evans-Lacko, Gruber, Sampson and Aguilar-Gaxiola1} versus annual suicide rates as reported by the World Health Organization. ³ In data available from 12 countries of greater versus 8 of lesser wealth listed by Thornicroft et al, ^{Reference Thornicroft, Chatterji, Evans-Lacko, Gruber, Sampson and Aguilar-Gaxiola1} annual suicide rates averaged 9.48 (95% CI 6.80–12.2) v. 5.31 (2.23–8.40) respectively per 100 000 (t = 2.27, P = 0.04). Rates of minimally adequate treatment of identified MDD cases differed correspondingly: 48.2% (40.9–55.5) v. 28.7% (14.0–43.4) among those who wanted treatment (t = 3.01, P = 0.008), and 23.4% (19.6–27.3) v. 7.36% (3.35–11.4) for MDD cases overall (t = 6.28, P<0.0001). Moreover, there was a strong, direct, linear correlation between greater rates of treatment (by either measure) and higher suicide rates (r _s = 0.644, P = 0.005; slope for rates of treatment of those wanting it: 0.154 (0.049–0.260), t = 3.09, P = 0.006).

These observations are sobering in indicating: (a) surprisingly low observed rates of minimally adequate treatment for MDD, especially in less affluent countries, and (b) absence of lower suicide rates with greater rates of treatment. However, we propose that the various numerical estimates involved are susceptible to errors of ascertainment. Notably, the relatively low reported suicide rates in less affluent regions may, at least partly, reflect incomplete reporting. Low observed rates of treatment, instead, probably reflect complex differences that may include ascertainment errors, less access to care (lower clinician density and economic factors) and cultural factors, between relatively wealthy and poor countries. Efforts to reduce morbidity and mortality, including reduction of suicide risks, by improving recognition and treatment of MDD are highly laudable. However, their demonstration may require relatively challenging, within-region outcome measures, such as valid comparisons of suicide rates before versus after interventions aimed at improving clinical care.