Introduction
The need to belong is an essential characteristic of human beings and a strong motive guiding our cognitions, emotions, and behavior [
1]. Although from an evolutionary perspective the importance of belonging nowadays might be less crucial for survival and reproduction as compared to our ancestors, it is still thought to be a critical factor determining people’s emotional well-being [
2]. When the need to belong is not satisfactorily met, feelings of loneliness may arise [
3]. Loneliness is a subjective and negative experience [
4] that derives from a discrepancy between the interpersonal relationships people desire and the quantity and quality of these relationships that are actually perceived [
5].
Loneliness involves intra-individual characteristics like self-esteem and shyness as well as inter-individual experiences referring to positive and negative peer interactions varying from social acceptance and friendship to bullying and victimization [
6]. Loneliness appears to be the result of a complex interplay between a person’s desires, social abilities, perceptions, and interpretations, and social interactions and thus reciprocal processes with others. While it is perfectly normal to feel lonely every now and then, it is also clear that persistent and increased feelings of loneliness have to be considered as clinically relevant. This is supported by research findings demonstrating that loneliness is associated with mental health problems, like anxiety disorders and depression, and even physical complaints and diseases [
3].
Loneliness is a prevalent phenomenon during adolescence and can be considered a common experience in this developmental phase [
3]. Adolescents might be more susceptible to feelings of loneliness for several reasons. During adolescence youths tend to shift from family to peers as their most important companions. While they become more individuated and autonomous towards their parents and involvement in the peer group becomes more important, they also have to handle their pubertal maturation and their identity formation process [
7]. Social interactions become more complicated, and the awareness of social competence of the self and others increases. During this transition, it might be quite difficult to fulfil their expectations about social relationships and to satisfy their need to belong resulting in loneliness at some point [
3]. For youngsters with autism spectrum disorders (ASD) it might be particularly difficult to keep up with their peers and to be involved with and accepted by them.
Deficits in communication and problems with social interaction are core characteristics of children and adolescents with ASD [
8,
9]. For example, youth with ASD have less social skills [
10], are more often victim of bullying [
11], experience poorer friendship quality [
12], spend less time interacting with others [
13], and have a less central position in social networks [
14,
15]. Given these social difficulties, one might expect that children and adolescents with ASD are at increased risk for experiencing feelings of loneliness. Several studies have shown that children and adolescents with ASD indeed report higher levels of loneliness relative to their non-clinical peers [
14,
16‐
20]. However, Chamberlain and colleagues [
21] did not find elevated levels of loneliness for younger children with ASD as compared to typically developing control children. It has been suggested that the experience of loneliness in youth with ASD might be age-dependent and becomes more pronounced during adolescence [
19]. In fact, previous studies that documented elevated levels of loneliness in relation to ASD mainly relied on samples that predominantly included adolescents [
14,
18‐
20]. Besides that, the sample sizes of these studies were often relatively small, and so in studies that did include younger children it was not possible to explore the experience of loneliness in youths with ASD of various ages [
16,
17].
Meanwhile, some scholars have suggested that youths with ASD have less desire for social interaction [
22] or a stronger wish to be on their own [
23], and as such children and adolescents with ASD might be less prone to develop feelings of loneliness. However, it should be noted that a stronger desire for aloneness and loneliness are not mutually exclusive [
3,
24]. In addition, previous research assessing the desire for social interaction in 7- to 12-year-old children with ASD demonstrated that these youngsters did show a desire for social interaction on an implicit level (as measured by means of an experimental approach-avoidance task), while they expressed less desire for social interaction on an explicit level (as assessed with a questionnaire) as compared to typically developing children [
25]. It might be that social deficits hinder youths with ASD to openly express their desire for social interaction. That is, it is possible that they do experience a desire for social interaction or a need to belong, but lack the skills and/or need specific circumstances in order to be able to translate this wish into action.
It is unclear whether increased levels of loneliness are specific for ASD or are more generally related to developmental disorders or psychopathology in youths [
19]. As mentioned before, loneliness is related to different types of psychopathology like depression and anxiety, but the direction of causality is still ambiguous and might also be bi-directional [
3,
26]. However, for other types of psychopathology loneliness is more likely to be a consequence rather than cause of the symptomatology. For example, it could be possible that youths with Attention Deficit Hyperactivity Disorder (ADHD) experience higher levels of loneliness, but loneliness alone is unlikely to cause ADHD. This makes youth with ADHD an interesting clinical comparison group, although it should be admitted that the studies conducted so far have yielded quite mixed results. Heiman [
27] documented increased levels of parent- and teacher-rated loneliness, but not on self-reported loneliness when comparing an ADHD group with a non-clinical control group. However, in a more recent study, Houghton and colleagues [
28] found comparable levels of loneliness in children and adolescents with ADHD and their typically developing counterparts.
In the present study we took a closer look at the phenomenon of loneliness in youths with ASD, adopting a multi-informant approach using assessments of children themselves, parents, and teachers. Three groups were included in this investigation: an ASD group, a clinical control group of youths with ADHD, and a typically developing control group. Each group consisted of children (i.e., age 7–11 years) as well as adolescents (i.e., age 12–18 years). It was hypothesized that (1) the ASD group would show increased levels of loneliness as compared to the typically developing and the clinical control group, and (2) adolescents would display higher levels of loneliness than children. In addition to loneliness, we also measured youths’ desire for social interaction, social skills, social problems, social competence, and social anxiety, which enabled us to explore their relation with loneliness. For these other social variables, we also made group comparisons. Here we expected to find (3) lower levels of desire for social interaction, lower levels of social skills and social competence, and higher levels of social problems and social anxiety in the ASD group as compared to both control groups. Our predictions regarding differences between the clinical and non-clinical control groups were less clear, but on the basis of what has been found in the literature it might be expected that children and adolescents with ADHD would show lower levels of social skills and social competence, and higher levels of social problems than their typically developing counterparts [
29‐
31]. Finally, the relations between loneliness and the other social variables were explored. Here it was hypothesized that (4) loneliness would correlate positively with desire for social interaction, social problems, and social anxiety, and negatively with social skills and social competence.
Discussion
In the present study, the phenomenon of loneliness in youths with ASD was examined in more detail. Children and adolescents with ASD completed a self-report questionnaire for measuring this construct and their scores were compared with those of a clinical control group of youths with ADHD and a non-clinical control group of typically developing children and adolescents. In line with the first hypothesis, the ASD group overall reported elevated levels of loneliness as compared to the clinical and non-clinical control groups, but this was mainly true for youths in adolescent age range. In fact, no significant differences between the three diagnostic groups were found in the younger participants. These findings are well in line with previous studies showing that youths with ASD are indeed more prone to feelings of loneliness and that, in comparison with clinical and non-clinical control groups, this problem becomes really manifest during adolescence [
14,
16‐
21].
In contrast to what has been suggested in the loneliness literature (hypothesis 2; [
3,
7]), the results of our study demonstrate that adolescents in general displayed lower levels of loneliness than children. One explanation for this unexpected finding is concerned with the fact that loneliness appears to be a multidimensional construct and that various aspects of loneliness may manifest themselves during different developmental stages [
3]. In relation to this point, it should be kept in mind that in the present study only one specific dimension of loneliness, namely peer-related loneliness. Maes and colleagues [
36] also noted that that this specific aspect of loneliness decreased from childhood to adolescence, whereas other dimensions of loneliness (i.e., parent-related loneliness) increased as youths became older. Another possibility is that children complete a measure like the LACA with a somewhat different perspective than adolescents, resulting in differential loneliness scores for both age groups. Finally, it is also possible that most adolescents are capable of successfully taking the developmental hurdle of connecting to the peer group [
46]. It should be borne in mind, however, that most studies on loneliness including the present investigation are cross-sectional in nature, and that more prospective research is necessary to test these possibilities. Interestingly, there is a recent longitudinal trajectory study in non-clinical youths (
N = 586) by Qualter and colleagues [
47] which shows that there are more young people who exhibit stable low (37%) or declining (23%) levels of loneliness for the interval between 7 and 17 years, whereas a minority of 22% and 18% display respectively stable high or increasing levels. It would be interesting to include youths with ASD in such a study and learn more about the developmental pathway of loneliness in youth with this developmental disorder.
In line with our previous study [
25], the ASD group exhibited lower levels of self-reported desire for social interaction as compared to the non-clinical control group, while the clinical control group scored in between. Overall, there was a significant effect of age group for this variable, which reflects that adolescents indeed have a stronger wish for social interaction than children [
7]. Interestingly, this age effect was not only observable in the clinical and non-clinical control groups, but also in the ASD group, which suggests that even these youngsters have a stronger “wish to belong” during the developmental stage of adolescence.
In keeping with hypothesis 3, statistically significant group differences were found with regard to the parent- and teacher-rated social variables. As expected, the ASD group displayed lower levels of social skills and social competence but higher levels of social problems and social anxiety as compared to the clinical and non-clinical control groups, which is hardly surprising given that deficits in social functioning are one of the defining features of autism spectrum problems [
8,
9]. On some of these social variables, the clinical control group also deviated significantly from the non-clinical control group. For example, according to the parents, children and adolescents with ADHD displayed lower levels of social skills and higher levels of social problems than typically developing youths. These findings are in line with previous research demonstrating that ADHD is also to some extent associated with social difficulties [
29‐
31,
48,
49].
The correlational analysis generally showed that the expected links between loneliness and other social variables. That is, negative correlations were found with social skills and social competence, while positive correlations emerged with social problems and social anxiety. These results are well in line with previous research showing that high levels of loneliness are associated with poor social skills, weak social competence [
3,
50], and high levels of social anxiety and other social problems [
51]. Most of these relationships are thought to be bi-directional in nature, indicating that on the one hand loneliness may be the result of poor social functioning, but that one the other hand loneliness is likely to promote social difficulties [
3]. To gain more insight in the role of loneliness in social functioning, especially in youths with ASD, it might be worthwhile to employ the experience sampling method (ESM). ESM repeatedly asks participants to record feelings, cognitions, and behaviors within the context of their daily life, and represents a very informative way to study psychopathology and related phenomena [
52].
The correlation between loneliness and the desire for social interaction was negative, which is on first sight surprising as one might expect loneliness to be coupled with a stronger wish to interact with other people. This seems to indicate that the relation between loneliness and desire for social interaction is more complex and probably subject to moderating variables. For example, it may well be that when combined with positive affect, feelings of loneliness may fuel the wish for social interaction, whereas feelings of loneliness which are associated with negative feelings (dysphoria, shyness, or social anxiety) may undermine the desire for social interaction and prompt withdrawal behavior. Other factors possibly involved are the chronicity of loneliness, victimization, children’s self-esteem, and the level of social skills [
3,
6].
As noted earlier, one drawback of this study was the cross-sectional design, which not only prevented the investigation of developmental trends but also hindered us in testing causal relationships between loneliness and other social variables. The role of loneliness in the social and emotional well-being of youths with ASD is likely to be rather complex, and requires a more elaborated, longitudinal investigation that should also include other relevant variables such as depression [
53]. A further limitation of the present study was the lack of standardized instruments for diagnosing ASD (e.g., Autism Diagnostic Interview-Revised; [
54]), ADHD, or comorbid psychopathology (e.g., Structured Clinical Interview for DSM-IV Childhood Disorders; [
55]) in the clinical groups. Note in passing that almost one quarter (i.e., 23.3%) of the children and adolescents in the ASD group also had a diagnosis of ADHD, which of course somewhat obscures the comparison with the clinical control group that consisted of youths who had a primary diagnosis of ADHD (but no ASD). The coexistence ASD and ADHD is a common phenomenon [
56], and in spite of the fact that we did not control for this diagnostic overlap, we did document significant differences in loneliness and other social variables between these two groups, which of course suggests that the presence of ASD was the determining factor. Another shortcoming pertains to the fact that DSM-IV-TR diagnoses were still used in the present study [
8]. Since the majority of the youth in the ASD group were diagnosed with PDD-NOS, it might be that not all participants of the ASD group would fulfill the DSM-5 (
Diagnostic Statistical Manual of Mental Disorders, fifth edition; [
9]) criteria for ASD [
57,
58]. Our ASD group can best be considered as a high-functioning ASD group with mild to moderate ASD symptoms in terms of the DSM-5. A final demerit has to do with the unequal gender distribution across the three groups: the ASD group and the clinical control group of youths with ADHD clearly contained more boys than girls [
33,
34], whereas in the nonclinical control group the gender distribution was more equal. Available studies suggest that there are no pronounced differences in loneliness between boys and girls [e.g.,
36], but it should be admitted that research in clinical samples (such as youths with ASD) is lacking and so this remains a topic of future inquiry.
The results of the present study are also relevant for clinical practice. Loneliness seems to be a rather overlooked problem that deserves more attention. Clinicians should focus more on understanding the implications of social impairments and the unmet desire for social interaction in youths with ASD. These youngsters often have a learning history of social failure and disappointment and might simply give up and choose to protect themselves against future difficulties by means of withdrawal and avoidance behavior, thereby becoming trapped in isolation and feelings of loneliness [
59]. Interventions that enhance social skills might be of great value. In fact, it has been demonstrated that social skills training for children with ASD can successfully decrease feelings of loneliness [
60]. It is recommended to implement this type of intervention before the transition from primary to secondary school so that children are better equipped to face the social challenges of adolescence.