The main aim of this study was to evaluate the mediating effect of adolescent emotional and behavioral problems (internalizing and externalizing) on the relationship between having an ASD diagnosis and perceived quality of life in emerging adults. Only internalizing problems turned out to mediate the relation between ASD and PQoL. After adding internalizing problems as a mediator, the direct effect of ASD on PQoL did not reach statistical significance.
First, we found that having a diagnosis of ASD significantly predicted poorer PQoL in emerging adulthood. This is also in line with previous findings of the relationship between autism and subjective QoL (6, 12, 13, 15) and contrast to findings of Chiang and Wineman (22) and Oakley et.al. (18). Our study expands on previous findings by demonstrating that ASD is associated with reduced PQoL in a sample of emerging adults who were diagnosed with ASD in childhood. Emerging adulthood is characterized by fundamental changes within personal, social, emotional, neuroanatomical, and developmental levels. Parallel with these changes and expectations of increased independence, familial and institutional support is gradually withdrawn. As a result of this, emerging adulthood can be considered a critical phase in human development with a significant impact on adult outcomes (48). While the findings are inconsistent, some studies have suggested that higher age is associated with lower QoL in individuals with autism (13, 49). Therefore, it is important to investigate QoL within specific developmental periods, such as emerging adulthood. Previous studies have also had the limitation of investigating samples with a wide age range, spanning several developmental stages of adulthood (see 50 for a review). Furthermore, lower levels of PQoL among individuals with autism emphasize the importance of identifying factors associated with this reduction. Studies of potential mediators and moderators are especially valuable because, by identifying mediators and moderators, we can better develop and target interventions for improving PQoL among individuals with autism.
The hypothesis that internalizing problems in adolescence would mediate the relationship between childhood ASD and PQoL in emerging adulthood was supported. This corroborates previous studies, which consistently have found a negative association between internalizing problems and QoL in adults with autism (see 50 for a review). However, unlike previous studies, we tested the mediation effect of internalizing problems on the relationship between ASD and PQoL in a longitudinal design. The results from our analyses showed that when accounting for internalizing problems, ASD was no longer reliably associated with reduced PQoL. Internalizing problems fully mediated the relationship between ASD and PQoL. This expands on the cross-sectional findings of Reed et.al. (29) demonstrating that social anxiety, depression, and loneliness fully mediated the relationship between autistic traits and subjective QoL in a group of university students. Our findings clearly emphasize the need to target internalizing problems among adolescents with ASD. These findings are important as individuals with autism have been found to suffer from a higher burden of psychopathology symptoms across the lifespan than other clinical groups (51). Previous findings from our sample have highlighted the persistence of internalizing problems from childhood into emerging adulthood among individuals with autism (27). Adults with autism have claimed that interventions in childhood are important for improved adult QoL (52). So, an important topic for future research is whether interventions targeting internalizing problems among children and adolescents with autism can contribute to better QoL in emerging adulthood.
Internalizing problems is critical to understanding QoL outcomes in adults with autism, but more research is needed to determine which factors influence internalizing problems at different stages of life. Better cognitive functioning in childhood seems to be associated with fewer problems with adult everyday functioning (53). Among emerging adults with autism, Hollocks et.al. (54) found that deficits in cognitive flexibility contributed to internalizing problems. As a result, the core deficits in executive functions demonstrated by many emerging adults with autism (32) may be relevant factors in understanding the elevated levels of internalizing problems and ultimately QoL. Furthermore, there may be specific factors influencing internalizing problems and QoL in the developmental phase of emerging adulthood. This is a period of transition from living with parents to more independent living. This transition is often accompanied by a shift in school (e.g., from high school to college) or from school to work, and there is also a shift in services. Studies have highlighted a possible drastic decrease in services during this phase (5). A large transition with increasing environmental demands, accompanied by a decrease in services and support, can lead to poor person-environment fit and consequently contribute to more internalizing problems and poorer QoL in emerging adults with autism, Qualitative studies have revealed that emerging adults with autism frequently face a lack of personalized support and experience situations that are inadequate in meeting their psychosocial requirements (52, 55). More research is needed within this domain to better understand, in-depth, the experiences of emerging adults with autism, and their needs for services and support.
In contrast to our hypothesis, the serial mediation showed no significant independent effect of externalizing problems on PQoL in either of the analyses. As there was a strong relationship between internalizing and externalizing problems, we expected both to act as mediators in succession, and that externalizing problems were affected by internalizing. This turned out not to be the case as there was no significant relation between externalizing problems and PQoL. One explanation for this may be that the level of externalizing problems was not very high in our sample. Externalizing problems T-scores for the ASD group were closer to the population mean and CG means than internalizing problems scores, and they were less correlated with ASD than internalizing problems were.
The broadband scale of internalizing problems on CBCL consists of three related, but distinct, subscales: anxious/depressed, withdrawn/depressed, and somatic complaints. As internalizing problems were found to have such a large impact on the relation between ASD and PQoL, we wanted to investigate how these three sub-scales acted in parallel mediation analysis. We found a significant relationship between ASD and all three subscales. However, the anxious/depressed subscale did not reach significance as a mediator between ASD and PQoL. This could be due to a higher level of symptom overlap between withdrawn/depressed and ASD than between anxious/depressed and ASD. Depression has been identified as a major contributor to reduced subjective QoL in people with autism (24, 25). Further, levels of depression in emerging adults with autism have been reported to be of similar magnitude to that of emerging adults with a primary depressive disorder (24). We have previously found a significant positive correlation between change in autism symptoms and change in depressive symptoms in our sample over two years (56). This indicated that autism symptoms and/or poor person/environment fit may lead to chronic conflicts, misunderstandings, and failures in professional life (57). As such, it is possible that ameliorating poor person/environment fit and depressive symptoms may not only lead to improved subjective QoL but also less perceived autism-related stress.
Somatic complaints are common among children experiencing trauma and are associated with anxiety (58). Ongoing potentially traumatizing school bullying or other adverse childhood experiences are relatively common among adolescents with autism and these are also more likely to present themselves as somatic complaints (59). It is a possibility that the somatic complaints reported here could be prodromal to later anxiety problems common in autism. The mediating effect of adolescence somatic complaints on later subjective QoL may be caused by somatic complaints in adolescent age developing into anxiety which hamper subjective QoL in emerging adulthood.
Implications and future directions
This study emphasizes the importance of assessing and treating mental health issues such as depression when seeking to improve the quality of life for emerging adults with autism. For the general public, symptoms of autism may be seen as the main driver of QoL for individuals with autism. Our study reveals that this is not necessarily the case. Mental health issues should therefore be considered as a comorbid trait with great importance for QoL and not as an inevitable part of having autism. This notion is following the findings of Joshi et.al. (51). Furthermore, they underline the importance of autism-specific interventions when treating comorbid psychopathology. However, there is no general agreement upon what constitutes a good QoL for people with autism (12). QoL may be perceived as something different for people with autism than for people in the typical population. Autism is commonly regarded as a disadvantage affecting QoL negatively, however, depending on the context, autistic characteristics can also be regarded by adults with autism as a strength, underlining the importance of person-environment fit (60, 61). It is important in the future to gain knowledge on how quantitatively measured difficulties affect perceived QoL and which factors constitute a good QoL for emerging adults with autism (62).
Limitations
One obvious limitation of this study is the relatively small number of participants. However, a notable strength is a relatively high retention rate over ten years (75% retention). Traditional measures of QoL such as the PQoL may not sufficiently tap into what QoL is for people with autism (55). Another limitation may be that our participants are drawn from a clinical population that has or has had greater psychosocial problems in their childhood. Still, we believe that the longitudinal design adds important knowledge on the relationship between having been diagnosed with ASD in childhood and QoL in emerging adulthood.