A study by the Instituto de Saúde Pública da Universidade do Porto (ISPUP) analysed mortality trends in Portugal for over 132 years and concluded that there are flaws in the registration of the number of suicide cases in the country.
The research, published in the Journal of Affective Disorders, found that the lower numbers of suicides recorded in certain periods of history may not be real.
The authors of the study, developed under ISPUP’s Epidemiology Research Unit (EPIUnit), analysed mortality data in Portugal between 1886 and 2018. They then investigated whether the trends in the number of deaths and suicides found over time corresponded to reality or were fictitious.
Overall, it was concluded that there was a downward trend in the number of suicides over the years in Portugal, with a greater decrease in three periods: in 1930, 1982 and 2001. However, the researchers found that the observed decrease in these three periods of history is fictitious, not corresponding to the reality of the cases that occurred.
Misregistration and changes in the disease classification system
The explanation for this decrease may reside “in the changes in the national statistical system and in the changes in the method of classifying diseases (nosology) during the indicated time periods”, explains Ricardo Gusmão, coordinator of the study, which has the co-authorship of Henrique Barros.
It should be noted that the change in the classification of diseases may have contributed to the increase in the so-called masked suicides (when death is not recorded as suicide, but as a consequence of another cause).
“The fact that many deaths by suicide are improperly registered makes suicide quite under-represented in Portugal. Such situation is worrying, as it contributes to diminishing the true dimension of this Public Health problem in the country,” he says.
Thus, it is necessary to be cautious when analysing the current suicide figures in Portugal and have a critical look at the conclusions of other studies on the subject.
“This work has shown that we need to improve the way we register suicides in our country. We realised that, at certain moments in history, there was an underreporting of the number of cases, giving the idea that the number of suicides was lower than it really was”, he stresses.
For the psychiatrist, this paper makes a kind of assessment of the existing data on suicide in Portugal, stressing that “it is only possible to be effective in preventing this Public Health problem when we can make a correct reading of the numbers”.
In this article, entitled Suicide time-series structural change analysis in Portugal (1913-2018): Impact of register bias on suicide trends, researchers Carlos Ramalheira, Virgínia Conceição, Milton Severo, Edgar Mesquita and Miguel Xavier also participated.