**1. Introduction**

Lung cancer is a very aggressive malignant disease; people who smoke or are exposed to polluted environments or with genetic mutation may be at significantly higher risk of lung cancer [1–3]. Published studies have shown that Asian women who never smoke still have a higher risk of lung cancer compared with women in European countries or the United States [4,5]. Based on a worldwide report issued by the International Agency for Research on Cancer in 2018, for both males and females, lung cancer had become the most prevalent cancer globally (with incidence rate of 11.6% of all cancers) and had been ranked as the leading cause of cancer death (death rate of 18.4% of the total cancer deaths). The economic burden of treatments and care for lung cancer has also globally increased in recent years [6,7]. Published studies have showed that lung cancer is significantly associated with older age (70 years old being the average age of initial diagnosis) [7,8], but very low incidence rate in young people aged 20–40 years around the world [8]. In recent decades, due to the dramatic improvements of clinical treatments and screening techniques for lung cancer, the survival of newly diagnosed lung cancer patients has been significantly prolonged [9,10] and the incidence rate in young patients with lung cancer also

**Citation:** Fang, Y.-W.; Liu, C.-Y. Determining Risk Factors Associated with Depression and Anxiety in Young Lung Cancer Patients: A Novel Optimization Algorithm. *Medicina* **2021**, *57*, 340. https://doi.org/ 10.3390/medicina57040340


Academic Editor: Camelia Diaconu

Received: 19 February 2021 Accepted: 24 March 2021 Published: 1 April 2021

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increased [1,5,8]. Published studies also showed that young patients with lung cancer had better treatment outcomes of receiving surgery, chemotherapy, or radiotherapy and have relatively longer relapse-free survival, which indicates that young lung cancer patients are more likely to have prolonged survival [11–13].

Therefore, young patients with lung cancer are a noteworthy group of patients, because they have obviously lower incidence rate and prevalence rate than middle-age or elder people and they may have longer survival time. Liu et al. (2019) [14] used a retrospective review of patients with lung cancer in one hospital in China from January 2010 to June 2017, the prevalence of lung cancer in young adults aged between 18 and 35 years old was 1.37%; and Rich et al. (2015) [15] also used a retrospective cohort review using a validated national audit dataset and the results showed that the prevalence of lung cancer in young adults aged between 18 and 39 years was 0.5%. The overall incidence and prevalence in elder age groups (>50 years old) was increasing in recent decade, however, the incidence and prevalence of lung cancer in young adults (<40 years old) can be still regarded as relatively low in nowadays global cancer epidemiology. Recent studies showed that young lung cancer survivors are also at a high risk of psychiatric diseases, such as anxiety and depression in the following years of survival [16–18]. However, most of the published studies used self-reported scales or questionnaires to measure anxiety and depression instead of using diagnoses by psychiatrists; therefore, the so-called depression or anxiety in published studies can solely regarded as depression symptoms or anxiety symptoms. For example, Yan et al. [17] showed that the anxiety and depression prevalence rates of lung cancer patients were 43.5% and 57.1% by using the Hospital Anxiety and Depression Scale (HADS), which look high proportions in lung cancer patients. In addition, if young lung cancer patients who may have prolonged survival and are at high risk of psychiatristconfirmed depression and anxiety, they will consume considerable medical resources due to the additional treatments for psychiatric diseases [6,19]. Nevertheless, there is still a lack of literature investigating risk factors associated with psychiatrist-confirmed depression and anxiety in young lung cancer patients. This study was aimed to develop a novel algorithm for identifying risk factors for psychiatrist-confirmed anxiety and depression in young lung cancer patients aged 20–39 years old by using the population-based database (National Health Insurance Research Database (NHIRD) in Taiwan), which can assist clinicians or young patients with lung cancer in preventing anxiety and depression at early stages.
