Research Involvement, Career Determinants, Study Experiences, and Personality Traits of Health-Care Students and Workers: The Research In-Depth Study Protocol.

COVID-19 caused significant changes globally, including lifestyle among adolescents. This study found self-reported fatigue increased among female adolescents in Finland utilizing cross-sectional surveys conducted before (2018) and after the COVID-19 pandemic (2023). Higher levels of internalizing and externalizing problems were associated with higher levels fatigue across both sexes. Fatigue is a common complaint among both adolescents and adults (–), characterized by tiredness, lack of energy, weakness and exhaustion (, , , ). While fatigue can be transient, it is also a prominent feature of several chronic illnesses including sleep disorders, cardiovascular and pulmonary conditions, neurological diseases, depression, cancer, autoimmune diseases, and sequalae from trauma like head injuries, among others (, , ). In addition, fatigue may result from viral infections, such as COVID-19, where it has emerged as a hallmark of long COVID (, ). Chronic Fatigue Syndrome/myalgic encephalitis (CFS/ME) includes the debilitating chronic and unexplained fatigue experienced by an individual over a prolonged period of time that overlaps with other symptoms like sleep problems, musculoskeletal pain, and concentration or short-term memory problems (). Fatigue in adolescents is of particular concern and rarely occurs in isolation; instead, it may affect education outcomes but could be interwoven with broader emotional and behavioural difficulties. For example, it can be attributed to factors such as, psychological stress, lifestyle changes, hormonal fluctuation, social demands, educational pressures, school attendance and performance contributing to absenteeism (). A systematic review focusing on long COVID-19 symptoms reported pre-COVID (1989–2019) found a pooled prevalence of 20.5% of fatigue from 4 studies among adolescents aged 10–19 years (). A third of adolescents aged 11–17 years reported morning fatigue occurring at least four times in a week in Europe in 1997/1998 (). Fatigue among adolescents is an important symptom, given its potential to impair both physical and mental well-being. Prevalence rates among adolescents in the general population vary widely, ranging from 7% to 38% in studies in the Netherlands, United Kingdom, United States, and Japan with higher rates reported among girls (, , , ). Furthermore, a prevalence ranging from 7% to 45% has been reported in the adult population (, , , ). Community studies show that youth who report higher fatigue levels also exhibit elevated internalizing symptoms, such as anxiety, depression, and somatic complaints, as well as externalizing behaviours including conduct problems and hyperactivity (, ). Clinical samples further demonstrate that sleep-related fatigue predicts both mood disturbance and behavioural dysregulation in adolescents seeking mental health services (). Moreover, emerging research on long COVID indicates that persistent fatigue among adolescents often co-exists with anxiety, low mood, and irritability, suggesting that post-infection sequelae may exacerbate underlying psychological vulnerabilities (, ).