According to research, supports are necessary for an adequate transition to adulthood, and appropriate functioning for people with autism. The design and execution of transition plans during high school as part of the Individualized Education Program (IEP), and transition to employment programs out of school, are supposed to make up for the diminishment or lack of intervention services for young people with ASD (including ASD-1). The aim of these services should be to train functional skills so this population can function independently (Anderson et al., 2022; Chandroo et al., 2018; Hurley-Hanson et al., 2020; Schall et al., 2014; Test et al., 2014; Wehman et al., 2014; Rydzewska, 2012).

As a main recommendation, transition plans and programs should be individualized (Anderson et al., 2018; Test et al., 2014), focusing primarily on the strengths, preferences, and interests of each person with ASD (Anderson et al., 2022; Schall et al., 2014). However, they should have certain objectives in common to promote better performance in adult life. Specifically, they should focus on developing skills such as self-determination, self-management, autonomy, professional development and adaptative behaviour (Anderson et al., 2022; Anderson et al., 2018; Chandroo et al., 2018; Kraemer et al., 2022; Schall et al., 2014; Test et al., 2014; Wehman et al., 2014).

About self-determination, it is crucial that people with ASD-1 learn to communicate their choices, ask for help, request breaks when they are overwhelmed, and maintain attention with people they are interacting with, among others. In terms of self-management of behaviour, it is essential that students with ASD learn to monitor their own behaviour and have their own support strategies. In terms of autonomy, it is important to help them acquire skills that they will need when they transition to adulthood (e.g., communication skills); to this end, it is vital that they are exposed to experiences in community, post-obligatory education and/or work environments to experience what it means to work in certain areas. In the professional field, coherence between strengths, preferences and interests with the chosen profession, and having clear employment goals, should be promoted. Finally, it is important to improve adaptative behaviour skills, because they are associated with a higher quality goals after graduating from school, that include employment, education and independent living areas.

Specifically, in high school settings, the access to recreational and leisure activities, that align with the interests and future goals of people withs ASD-1, should be facilitated. This would favour their learning about themselves and socialization (Test et al., 2014). Moreover, the design of transition plans should also ensure this population have access to learning opportunities that promote real growth, while considering their particular characteristics (Kraemer et al., 2022; Test et al., 2014). Therefore, it is important to guarantee a general education inclusion (Feldman and Daviso, 2018; Hurley-Hanson et al., 2020), where personalized supports and the provision of effective accommodations and instructions will be built up as they transition into adult life (Schall et al., 2014). Likewise, it is relevant to encourage their active participation in the planning and organization of transition plans so that they can aspire to continue with their academic training or enter the labour market once they finish secondary school (Hurley-Hanson et al., 2020; Kraemer et al., 2022; Wehman et al., 2014).

Outside of the school setting, it is crucial to maintain a support system through post-secondary transition programs, like vocational rehabilitation services or community rehabilitation programs (Hurley-Hanson et al., 2020; Schall et al., 2014), which should integrate, as some of their intervention targets: vocational counselling (Schall et al., 2014), interview skills training (Anderson et al., 2022), job placement assistance and on-the-job training and supports (Hurley-Hanson et al., 2020; Schall et al., 2014) that help ASD-1 people to secure and maintain a job.

The involvement of family, teachers, and peers is essential for people with ASD-1 to achieve better functioning in adult life (Barahona-Correa, 2017; Nicholas et al., 2017; Test et al., 2014). In the case of parents/tutors, they are expected to have a less active role, in order for their children to gain greater independence, without this meaning that all support resources must be withdrawn; rather, they are expected to have new role models (teachers, classmates, bosses, etc.) who can guide them in their transition process (Anderson et al., 2018). Finally, it is essential to continue raising awareness about ASD to promote an “autism-friendly environment” and a supportive culture (Anderson et al., 2018; Henninger and Lounds Taylor, 2012).

Considering the importance of the implementation of transition plans, Chandroo et al. (2018) conducted a systematic review on the level of participation of students with ASD-1 in this type of service; they found that they tend to be minimally active involved in the planning process or do not attend IEP meetings. The lack of clear information on the objectives and procedures to be followed during the meetings, and the lack of preparation of the educators responsible for supporting students with ASD-1, are two barriers detected. In reference to this last point, it seems to be few interventions and methods to train professional at improving the quality of goals of transition plans (Bahry et al., 2024). This is line with a study, where adults with ASD-1 reported being active in selecting colleges (where they subsequently attended), but they did not receive robust transition services in high school, specially, they missed experiences focused on developing independent living or social skills (Austermann et al., 2023).

In outside school services, research points out that a good support network lets ASD-1 people to have a more positive subjective transition experiences within educational or employment contexts (Davidovitch and Gerkerova, 2024; Wehman et al., 2014). In contrast, a lack of support its related with poor mental health (Anderson et al., 2022). Therefore, it is crucial to keep improving transition services.

In some studies, it has been found that only between 3 and 12 % of the population with ASD-1 completes university studies (Flower et al., 2021; Ojea and Diéguez, 2016). Additionally, a large majority are unemployed (Hurley-Hanson et al., 2020; Solomon, 2020) or work in positions that do not correspond to their educational qualifications, which tend to exceed the characteristics required for the job profile (Bruyere et al., 2020; Hurley-Hanson et al., 2020). In the realm of social relationships, less than half of adults with ASD-1 report having friendships or a romantic relationship despite their desire to interact with others (Henninger and Lounds Taylor, 2012; Howling and Magiati, 2017; Schall et al., 2014; Wehman et al., 2014). Finally, there are high percentages of adults with ASD-1 who depend on their parents, relatives, or the government for assistance (Henninger and Lounds Taylor, 2012; Howlin and Magiati, 2017; Schall et al., 2014), despite of emancipated living, in some cases (Howlin and Magiati, 2017), having a stable job or participating in social activities (Henninger and Lounds Taylor, 2012).

These outcomes are related with different factors, that have been grouped into demographic, neurocognitive, autism-intrinsic, socio-environmental, and other factors.

Demographic Factors. Eight articles analysed in the systematic review by Zimmerman et al. (2018) studied the relationship between age, gender, and functioning in adults with ASD-1. Only in one study did older age correlate negatively with social functioning. As similar finding was reported by Kirby et al. (2016), specifically between age and social relationship domain. In contrast, in the initial stage of the longitudinal study by Scheeren et al. (2022), older age predicted higher levels of social functional. Although, in the last stage, age did not predict more growth in social functioning. According to the authors, older adults may have had more time to reach certain milestones.

With respect to gender, in two reviews noting that men with ASD-1 are more likely to be employed or access post-obligatory education than women with ASD-1 (Howlin and Magiati, 2017; Zimmerman et al., 2018). They also reported greater well-being in their relationships compared to women (Zimmerman et al., 2018). However, recent studies find that women are more likely to have socially valued roles (like intimate relationships and post-obligatory education) than men, although more of them are also expected to have poorer mental and physical health too (Dubreucq et al., 2023). On the other hand, other studies did not find a significant relationship between gender and functioning in adults with ASD-1 (Kirby et al., 2016; Mason et al., 2020; Scheeren et al., 2022).

Neurocognitive Factors. Most literature reviews and systematic reviews mention that there is a consistent correlation between intelligence quotient (IQ) and social functioning in adults with ASD (Howlin and Magiati, 2017; Kirby et al., 2016; Levy and Perry, 2011; Zimmerman et al., 2018). However, a recent meta-analysis concluded that while higher IQ is a protective factor against poor functioning, it is not a consistent predictor of good functioning (Mason et al., 2020). Therefore, although some adults with ASD-1 with preserved IQ manage to live partially independent lives, they may still experience significant obstacles in other aspects of their lives (Posar and Visconti, 2019; Ratto and Mesibov, 2015). It is common, for example, that they are able to get a job, but have difficulty keeping it (Barahona-Correa, 2017; Mason et al., 2020), due to the challenges inherent to the diagnosis of ASD. On the other hand, it is possible that early diagnosis of ASD together with the supports received moderates the relationship between higher IQ and better functioning (Scheeren et al., 2022).

Regarding other neurocognitive factors, Zimmerman et al. (2018) found a positive association between social cognition and the quality of interpersonal relationships. Bishop-Fitzpatrick et al. (2016) observed that adults with ASD-1 who scored better on executive function tasks reported better functioning in the workplace and better mental health. However, most of them continued to live with their families and depend to some degree on them. These results are in line with those described in the review by Hume et al. (2014), which points out that difficulty in independent functioning is related to a deficit in executive functions.

Early language development (Howlin and Magiati, 2017; Levy and Perry, 2011; Posar and Visconti, 2019) and cognitive language use (Dubreucq et al., 2023) also appear to be significantly related to improved social functioning in adults with ASD-1. Although, cognitive language use was also related with higher frequency of co-occurring mental problems, possibly because verbal ability its related with a higher insight into autism-related challenges (Dubreucq et al., 2023).

In the study by Otsuka et al. (2017), a multiple linear regression analysis revealed that adaptive behaviour was the only significant predictor of social functioning, explaining 64 % of the variance. On the other hand, Bishop-Fitzpatrick et al. (2016), applying a multimodal logistic regression model, found that better performance in daily living skills (adaptive behaviour dimension) predicts adults with ASD-1 being among the “best independent living” group.

Intrinsic Factors of Autism. The level of severity of ASD symptomatology is considered a predictor of difficulties in social functioning (Dubreucq et al., 2023; Howlin and Magiati, 2017; Helles et al., 2017; Hume et al., 2014; Kirby et al., 2016; Scheeren et al., 2022; Zimmerman et al., 2018). Therefore, it is expected that adults with ASD-1, who have milder symptoms, will have better functioning, compared to those with ASD with more severe symptoms.

In fact, some studies that have looked at the level of functioning according to the DSM IV classification of autism, concluded that classic or infantile autism has a greater relationship with poor or very poor functioning, compared to those with Asperger’s Syndrome (AS), high-functioning autism or atypical autism (Posar and Visconti, 2019). These results are in line with the meta-analysis by Mason et al. (2020) in stating that although not enough data were obtained to determine whether the autism subtype was a good predictor of functioning, a low proportion of participants with classic autism belonged to the “good functioning” group, while those who were diagnosed with ASD (which included AS) were less likely to belong to the “poor functioning” group.

However, it is common that people with ASD-1 keep showing difficulties in achieving and maintaining friendships or a partner (Helles et al., 2017; Ratto and Mesibov, 2015), getting a job or living independently (Helles et al., 2017) due to their difficulties in social communication. Moreover, they tend to be diagnosed with mental health diagnosis such as depression and anxiety (Howlin and Magiati, 2017; Levy and Perry, 2011; Posar and Visconti, 2019), despite presenting improvements in ASD symptoms.

Socio-environmental Factors. To have a more objective view of the social functioning of adults with ASD-1, the influence of family, school, and society has been studied (Anderson et al., 2018; Henninger and Lounds Taylor, 2012).

There are findings in regards to the educational level of parents (Zimmerman et al., 2018), their socioeconomic level, the expectations they have of their children with ASD-1 and their level of involvement in their education (Bishop-Fitzpatrick et al., 2016; Kirby et al., 2016) is associated with higher odds of getting a job in adulthood. It is crucial that during the transition process to the adult life of their children with ASD-1, parents adjust to the challenges of this stage since, otherwise, they could limit them in their process of achieving good functioning (Anderson et al., 2018).

On the other hand, the positive perception of “informal” support (from friends, the community, etc.) also seems to be related to better social functioning, specifically with better affective relationships (Zimmerman et al., 2018).

Finally, support services, such as career counselling, have also been found to be predictors of good functioning (Kirby et al., 2016). It is important that these are tailored to the individual needs of people with ASD-1 as they could otherwise be limiting (Anderson et al., 2018).

Other factors associated with functioning. It is possible that the concept of good functioning does not fit with the needs that are relevant to people with ASD, so it is suggested to measure factors that reflect the perception of this population regarding their living situation (Henninger and Lounds Taylor, 2012; Howlin and Magiati, 2017).

Scheeren et al. (2022) found a positive relationship between subjective quality of life (related to satisfaction) and social functioning, at least in the first two years of follow-up. However, in a two-decade follow-up study, adults with ASD-1 reported adequate subjective quality of life, despite most did not live independently or have full-time employment (Helles et al., 2017).

Bishop-Fitzpatrick et al. (2016) found that good functioning does not necessarily imply having an objective good quality of life (measured through indicators of physical health, mental health, neighbourhood quality, and family contact), and vice versa. In fact, adults with ASD-1 who lived independently and had a job reported greater mental health problems. However, more recent studies found a relationship between low levels of quality of life (highlighting the mental health indicator) and a poor social functioning (Dubreucq et al., 2023; Leader et al., 2021; Scheeren et al., 2022)

Studies indicate that adults with ASD-1 tend to score significantly lower in the domain of “socialization” (Matthews et al., 2015; Williams et al., 2014). In particular, the subdomain of “interpersonal relationships” or “social relationships” appears to be a substantial weakness (Kenworthy et al., 2010; Kraper et al., 2017; Matthews et al., 2015); Therefore, they tend to have significant difficulties in establishing friendships, in pragmatic language, awareness of emotions, social judgment, and courtesy skills. A study using WHODAS also found that in domains involving interaction with others, adults with ASD-1 presented significant difficulties compared to their neurotypical peers (Schmidt et al., 2015).

In the “daily living skills” (DLS) domain, adults with ASD-1 tend to excel (Matthews et al., 2015, 2017; Otsuka et al., 2017; Schmidt et al., 2015) and may even achieve similar performance as their neurotypical adult peers (Schmidt et al., 2015). On the other hand, Bal et al. (2015), in a longitudinal study, found that the progress of DLS (measured with the Vineland) slows down when transitioning to adult life. For these authors, the results would reflect changes in the expectations of family members (who play the role of informants) and would not necessarily mean a loss of skills.

Performance in each of the DLS subdomains appears to vary and be influenced by the type of test used. In the study by Kraper et al. (2017), adults with ASD-1 excelled in the subdomain “domestic life”, measured by the ABAS, and their performance in the subdomains “utilization of community resources” and “health and safety” was considered a relative strength. When the Vineland was used, they performed substantially lower in the “community” subdomain, which involves the skills to function autonomously in the place where one lives, the planning and organization of daily activities, and the knowledge of citizens’ rights and duties (Matthews et al., 2015). On the other hand, Bal et al. (2015) observed that performance decreases especially in the subdomain “domestic skills” when transitioning to adult life. It is possible that these differences between study results are related not only to the use of different assessment instruments, but also to the number of participants and their ages.

In the case of the “communication” domain, adults with ASD-1 significantly excelled in the “written language” subdomain (Kraper et al., 2017; Matthews et al., 2015).

Some longitudinal studies have found that, although the levels of adaptive behaviour achieved by adults with ASD-1 are lower than those achieved by their neurotypical peers, there is a trend towards significant improvement as they transition into adulthood (Bal et al., 2015; Tomaszewski et al., 2019; Zukerman et al., 2022).

To better understand which factors, influence a higher or lower level of adaptive behaviour, the role of different sociodemographic, psychological, and environmental variables was analysed.

Demographic Factors. Several studies have explored the relationship between age and the level of adaptive behaviour. Matthews et al. (2015, 2017) found that adults with ASD-1 have worse communication and social skills than their adolescent peers with ASD-1. In addition, the difference in levels of adaptive behaviour is greater between the group of adults with ASD-1 and their neurotypical peers than that between adolescents with ASD-1 and their peers without ASD. According to these authors, these results indicate that the adaptive behaviour of people with ASD-1 does not develop at the rate of chronological age and that this difference increases over the years (Matthews et al., 2017).

Despite these results, comparative analysis between the scores of adolescents and adults with ASD-1 in each of the questions that make up each domain of adaptive behaviour, shows that adults obtained better scores (therefore, better independent functioning) in four items of the “communication” domain, nine of the “daily living skills” domain and five of the “socialization” domain, compared to that of their adolescent peers (Matthews et al., 2017). They concluded that people with ASD-1 do not lose adaptive skills with age, but develop them more slowly, especially those corresponding to the domains of “communication” and “socialization” (Matthews et al., 2015).

Williams et al. (2014) found that adults with ASD-1 (ages 21 to 46) scored significantly higher than their school-aged peers (ages 8 to 12) in the “daily living skills” domain. The authors point to the possibility that there is a positive influence of intervention programs on daily living skills. However, more longitudinal studies are needed to analyse this issue in greater depth.

On the other hand, Kenworthy et al. (2010) and Kraper et al. (2017) found no significant correlations between age and adaptive behaviour. In both cases, ABAS was used as a measuring instrument.

Neurocognitive Factors. Similar to studies in children and adolescents (Alvares et al., 2020; Kanne et al., 2011), the intelligence quotient (IQ) of the adult population with ASD-1 tends to be significantly higher than the level of adaptive behaviour (Kenworthy et al., 2010; Kraper et al., 2017; Matthews et al., 2015). It has also been observed that the gap between the two constructs tends to increase with age (Matthews et al., 2015). Despite these results, a significant correlation has been found between IQ and adaptive behaviour (Otsuka et al., 2017), especially with the domains “communication” (assessed with the Vineland scales) (Matthews et al., 2015) and “conceptual” (measured with the ABAS) (Kenworthy et al., 2010; Zukerman et al., 2022). In terms of communication skills, IQ was positively correlated with performance in the “writing skills” subdomain. It also appears that these correlations are consistent from childhood to adulthood (Kenworthy et al., 2010; Matthews et al., 2015).

The longitudinal study by Bal et al. (2015) concluded that receptive language, together with nonverbal IQ and symptomatology level, predict a better level of daily living skills in the ASD-1 population. Different executive functions measured with the BRIEF (such as self-regulation, metacognition, cognitive flexibility, organization, and planning, among others) positively correlated with scores in adaptive behaviour measured with the ABAS obtained by youth with ASD-1 (Peterson et al., 2015; Sullivan et al., 2024). Some authors hypothesize that low executive functions may explain the gap between IQ and adaptive behaviour in people with ASD-1 (Matthews et al., 2017). However, recent research found that executive function accounted for only 3.4 % of the variance in adaptative behaviour (Sullivan et al., 2024).

Williams et al. (2014) studied the performance on measures of conceptual reasoning, problem-solving, and adaptive behaviour of adults with ASD-1 and neurotypical, and the relationship between these variables. They found that, in the experimental group, one of the components of conceptual reasoning, “flexible thinking,” correlated positively with adaptive behaviour, whereas, in the control group, the correlation between these constructs was negative. Therefore, it is possible that difficulties in cognitive flexibility better explain difficulties in adaptive behaviour in the ASD-1 population. However, they also noted that the experimental group showed similar performance to their neurotypical peers in problem-solving tasks, which were evaluated in laboratory environments, in a predictable and controlled manner. Therefore, it could be hypothesized that difficulties in cognitive flexibility are only seen in real-life situations (Williams et al., 2014).

In the field of social cognition, a positive correlation was found between adaptive behaviour and emotion recognition (Hudepohl et al., 2015; Otsuka et al., 2017). Hudepohl et al. (2015) pointed out that a low score in the domain of “socialization” would be better explained by a deficit in the perception of emotions and, therefore, it would be important to include it as an intervention objective. On the other hand, Otsuka et al. (2017) found that the perception of emotions explained 35 % of the variance in adaptive behaviour, constituting a significant predictor. In relation to this, Hervas and Romarís (2019) mention that adults with ASD-1 tend to use compensatory strategies to minimize their difficulties in social cognition.

Finally, positive correlations were also found between adaptive behaviour and other neurocognitive dimensions such as long-term memory, processing speed, and verbal fluency; the latter was a significant predictor of adaptive behaviour, explaining 47 % of its variance, with the perception of emotions being the main mediator between them (Otsuka et al., 2017). According to the authors, one possible interpretation is that, in adults with ASD-1, high verbal fluency would contribute positively to the processing of other people’s emotions, which would impact adaptive behaviour.

Intrinsic Factors of Autism. The correlation between adaptive behaviour and ASD symptomatology seems to be influenced by the diagnostic instrument used. For example, Kenworthy et al. (2010) found a negative correlation between the “communication” domain of ADOS and all domains of ABAS; however, they found no correlations between symptomatology measured with the Social Responsiveness Scale (SRS) and ABAS components. On the other hand, Kraper et al. (2017) found that the correlation between adaptive behaviour (assessed with the ABAS) and ASD symptomatology (measured with the SRS) was mediated by the mental health variable. In this way, they concluded that a high level of symptomatology is related to mental health problems, and that these two variables, in turn, have a negative impact on the adaptive functioning of adults with ASD-1. These findings are congruent with those of Schmidt et al. (2015), who suggest that mental health problems, such as anxiety and depression, correlate with low psychosocial functioning. In turn, improvements in adaptive behaviour are related to improvements in mental health (Zukerman et al., 2022).

On the other hand, it seems that autism symptomatology influences negatively in the effective use of compensatory resources to function adequately in their environment. For example, an adult with ASD may have difficulty using imitation as a resource to resolve a situation in which it is not clear what to do (Hervas and Romarís, 2019).

Socio-environmental Factors. Tomaszewski et al. (2019) conducted a longitudinal study, where one of the objectives was to measure the influence of the educational environment on the adaptive behaviour of young people with ASD (from 14 to 20 years old, 72 % had ASD-1). They found that those who scored high on the “independence” domain of the Autism Program Environment Rating Scale (APERS) improved their communication skills and daily living skills. Recent research found similar findings in young adults who participated in a training program, but in this case, improvements were in overall adaptative behaviour skills (Louksy et al., 2024). These findings were replicated in university students with ASD-1, who improved their communication skills after one year of participating in an integration program (Zukerman et al., 2022). Therefore, the support strategies employed by the mentors seem to have a positive influence on the adaptive development of this population.

Other factors associated with adaptive behaviour. Schmidt et al. (2015) found that the “participation in society” domain of the WHODAS is related to life satisfaction. Therefore, the ability to participate in social or community activities, and the barriers experienced from the environment are what influence the degree of satisfaction of adults with ASD-1.