Recognizing continued development beyond the adolescent years: Clinical child psychology and psychiatry spans early adulthood

What ‘adolescence’ is

‘Adolescence’, derived from the Latin adolescere, means ‘to grow to maturity’ (Shute & Slee, 2015) and is generally considered to be the developmental stage that begins with the onset of puberty and ends with the transition to adulthood. What constitutes ‘adolescence’ has been operationalised in different ways in the literature. Whilst the World Health Organisation defines adolescents as those aged between 10 and 19 (WHO, 2020), it also defines young people as up to age 24, aligned with others who have argued for a broader definition of adolescence that is more inclusive (age 10–24) and captures the biopsychosocial development that occurs between childhood and adulthood (McGorry et al., 2024; Sawyer et al., 2018).

Brain development continues to age 25

Adolescence is characterised by increased risk taking, impulsivity and emotional reactivity (Steinberg, 2008), which can be explained by brain development and is not complete until the mid-twenties. The prefrontal cortex, critical for planning, decision-making, and impulse control, continues to develop until approximately age 25 (Dumontheil, 2016). Specifically, neuroimaging studies have shed light on the dramatic cortical white matter development and grey matter pruning processes which take place (Blakemore, 2012; Fuhrmann et al., 2015). Over the course of adolescence and young adulthood, cognitive control (also known as executive functioning) increases (Dahl, 2004), which enables emotional recognition and regulation (Chan & Rawana, 2021; Ciarrochi et al., 2008; Zimmermann & Iwanski, 2018), metacognitive abilities, goal-directed and adaptive behaviour and improved impulse control. Working memory capacity, particularly the ability to monitor, manipulate and integrate complex information, also improves considerably, which enables better organisational ability (Blakemore & Choudhury, 2006; Crone & van Duijvenvoorde, 2021; Duell et al., 2018; Steinberg, 2008).

This neuropsychological reality has practical implications. When we design interventions for 18–25-year-olds, we are working with brains that remain highly plastic and responsive to both positive interventions and environmental stressors. Treatment approaches that recognize this neuroplasticity, for example by providing skills training, structured support during stress, and opportunities for positive development, can harness this window of opportunity (Fuhrmann et al., 2015).

The extended road to independence

The path to adulthood has fundamentally changed over recent decades. Young people typically spend longer in education, start careers later, remain financially dependent on parents for longer, and delay milestones like marriage and homeownership compared to previous generations (Sawyer et al., 2018). These changes are not just social preferences, they reflect economic necessity, given rising housing costs, competitive job markets, and the increasing requirement for higher education which have delayed the transition to independence (Sorgente et al., 2024). The COVID-19 pandemic further disrupted these pathways, disproportionately impacting young adults compared to older adults (Pierce et al., 2020).

During adolescence, peers and social acceptance become much more important and are influential in the development of the individual's self-identity separate from that of their family of origin (Lansford & Banati, 2018; Orben et al., 2020). Adolescents are particularly vulnerable to effects of social stress as their fear extinction learning is blunted (Pattwell et al., 2012). Adolescence involves transitions in social roles which involve increasing independence, autonomy, and responsibility (Lansford & Banati, 2018; Sawyer et al., 2012) and this continues into early adulthood (Branje et al., 2021; Wright & von Stumm, 2025).

For practitioners and service providers, this means recognizing that 18–25-year-olds often juggle complex, in-between identities. Legally, they are adults but frequently are still financially and emotionally dependent on family. They are developing their independence, yet still need support, and are navigating further education, early careers, and relationship formation simultaneously. Therefore, the extent to which it is useful to extrapolate from the adult literature is limited due to the developmental differences of this life stage.

Mental health vulnerability peaks in early adulthood

The statistics paint a clear picture; mental health difficulties reach peak prevalence in the late teens and early twenties. A comprehensive meta-analysis by Solmi et al. (2021) examined age-of-onset patterns across mental disorders, confirming that most mental health conditions first emerge before age 25. Anxiety disorders often emerge in childhood and adolescence, followed by peaks in mood disorders, eating disorders, and psychosis in the late teens and early twenties.

Despite this heightened vulnerability in young adulthood, this age group often experiences the poorest service access (Cadigan et al., 2019). For practitioners working with this age group, these findings emphasize the importance of making services accessible and appealing to young adults, including by considering practical issues like appointment times that accommodate study or work commitments, communication preferences, and attention to privacy concerns.

What the journal values

CCPP aims to bring together clinical practice and applied research focusing on understanding mental health and wellbeing, including treatment issues, for children adolescents and young adults, aged 0 – 25 years. Therefore, CCPP has consistently published work that prioritizes practical, clinically relevant research, including person-centered approaches that respect young people's autonomy and perspectives, and are developmentally sensitive to the unique needs of different age groups. Many papers published in the journal report on innovations in treatments that reflect the evolving biological and psychosocial understandings of development, including for specific groups who are disproportionately vulnerable to developing mental health problems.

This editorial builds on this foundation and calls for further advancement of the evidence base in several areas:

(1) Implementation science studies: To narrow the gap between research and practice, implementation science studies focused on methods and strategies to promote the integration of research findings and evidence into healthcare policy and practice could further improve outcomes. One example could be research examining different models for extending services across the adolescent-young adulthood transition —from complete integration (i.e. 12-25 ‘youth’ services, like Kooth (Hanley et al., 2021) and Headspace (Rickwood et al., 2019)) to enhanced transition programs (e.g. Singh et al. (2023) with attention to what works in different contexts and for different populations.

Child Clinical Psychology and Psychiatry welcomes submissions in these priority areas to build the evidence base for developmentally appropriate services spanning adolescence and emerging adulthood.

Conclusion

The evidence across neurodevelopmental, psychological, social, and epidemiological domains strongly supports extending youth mental health services to age 25, recognizing contemporary developmental realities. As researchers and practitioners, we have ethical and clinical obligations to advocate for service structures that reflect developmental evidence rather than administrative convenience. The current arbitrary transition at age 18 creates artificial barriers when young people face maximum vulnerability and need consistent support. Child Clinical Psychology and Psychiatry has long championed developmentally appropriate, evidence-based approaches to improving young lives. Extending this perspective through the transition to adulthood represents a natural evolution of our field, offering the potential to transform outcomes during this critical life stage. The ultimate measure of success will be young people receiving the right support, at the right time, in the right way, regardless of their age.