We present the results of a large cohort study based on a national population of over fifty thousand AYA diagnosed with 34 malignancies.

The main finding of our study is that AYA has a 2.39-fold higher risk of suicide after a cancer diagnosis than the general population of 15–39-year-olds. This is an isolated observation in the European context. A large English study showed no significant differences in the risk of suicide among cancer patients aged 18–39 compared with the general population [13]. Similarly, a Lithuanian study found no significantly increased risk of suicide among patients aged 15–49 [14]. Additionally, analyses conducted in Denmark did not identify an increased risk of suicide among patients aged 0–49 years [15]. In contrast, two American studies showed a 34 times/37 times higher risk of suicide in the group of 15–39-year-olds with cancer compared to the general population [9, 16]. It is difficult to hypothesize why the Polish AYA differ from the other European AYA. Exploratory research is needed to identify the causes of the psychological burden of Polish AYA and to identify possible deficiencies in oncological care provided to this group of patients.

To the best of our knowledge, this is the second largest AYA cohort with malignancy in which suicide risk was assessed. The largest cohort came from SEER and was used in two independent AYA-concerning studies [9, 10] that presented divergent observations, making interpreting and comparing their results with ours somewhat challenging. The added value of our study in the context of the existing literature is the exceptionally granular assessment of suicide risk in the AYA population after cancer diagnosis. This is the first study to quantify the risk of suicide in 34 malignancies in this age group, and the first study to stratify this risk over time from diagnosis.

In detailed analyses, we identified men diagnosed with testicular cancer as a suicide risk group, especially in 2–3 and 5–10 years after diagnosis. No previous literature has described the risk of suicide after a diagnosis of testicular cancer among AYA (independent of how it was defined). However, in studies concerning the entire population of cancer patients, regardless of age, the results differed by country. In England and Norway, no significant differences were found between suicide rates among patients with testicular cancer and the general population [13, 17]. However, such differences were found in the USA, where the SMR of suicide after the diagnosis of testicular cancer in the period < 1 year from the diagnosis was 6.31 (95% CI 1.30 to 18.43), after 1–5 years SMR was 11.63 (95% CI 7.59 to 17.03), and > 5 years SMR was 17.66 (95% CI 13.94 to 22.07) [16].

Men diagnosed with testicular cancer are significantly more likely to experience anxiety and depression [18, 19]. In a detailed study on the risk of suicide after a diagnosis of testicular cancer based on SEER data, only age < 30 years was associated with an increased suicide risk [18]. Race, marital status, stage, and decade of cancer diagnosis were unrelated [18]. It is difficult to determine the reasons for the increased risk of suicide in this group of patients unequivocally. However, the fact that both our analysis and the American study [16] showed an increase in risk over time after diagnosis allows for diverse hypotheses. Physical-, mental-, and job-related problems, as well as shifting outlooks on life and at work, may affect personal and professional judgments among long-term survivors of testicular cancer [20], which, in the broader perspective, may be linked to increased suicide risk.

The main advantages of the present study include coverage of the entire national population (representability and generalizability), large study population (over fifty thousand individuals), and calculation model (age–sex–year-SMR). Even so, the study did not have enough power to identify groups of women at an increased risk of suicide at particular cancer sites. In addition, although statistically significant, some of the results were based on individual events, and in such cases, the chance findings cannot be ruled out. Therefore, although we present these results in the supplementary materials, we do not draw any conclusions based on them. We do not propose that they should become the basis for making decisions about changes in clinical practice regarding the care of AYA with cancer. An extensive international study of a larger population could provide more information about particular risk groups. In addition, a limitation may be that, as in other studies based on large cohorts sourced from national registries, we had no access to history of substance use and pre-existing mental health diagnoses, which are examples of potential confounding factors.