This study aimed to examine the relationship between socioeconomic factors and the expression of hikikomori. The data were collected 8 times over a period of 10 years, and have a major limitation in that it is not clear how many participants overlapped between the data collection points (i.e., annually). Even with this limitation, the findings of the current study are important, as it is the first study to demonstrate a relationship between socioeconomic factors and the expression of hikikomori, which affects a reclusive and hard-to-access clinical population.
In the current study, many individuals with hikikomori were long-term cases, compared with previous research targeting 18- to 34-year-olds in France (mean duration = 29 months; [9]) and 16- to 35-year-olds in Japan (mean duration = 4.3 years; [5]). However, recent epidemiological studies in Japan have shown that 34.7% of individuals with hikikomori aged between 15 and 39 years have had the disease for more than 7 years [25, 37], while 38.2% of those aged between 40 and 64 years have had hikikomori for more than 7 years [26]. The duration of hikikomori in this study was similar to the aforementioned findings. The gender ratio of about 80% male was also similar to that in several previous studies in Japan and elsewhere—a ratio of 76.6% male was determined by the Japanese Cabinet Office [26], 80% by Chauliac et al. [9], 76.4% by Funakoshi and Miyamoto [38], 74.8% by Kondo et al. [5], and 75.6% by Lee et al. [20]. A possible reason for this gender ratio is the Japanese socio-cultural background, in which men typically experience more work-related psychological pressure than women do [39]. School non-attendance showed almost the same correlation coefficient as hikikomori. The relationship between school non-attendance and unemployment rate supports previous research [40]. As both showed a low correlation coefficient, further research is needed to clarify the reason for this. For example, school non-attendance, unlike hikikomori, may occur indirectly due to economic and psychological changes in the family as a result of parental unemployment, and may often involve antisocial behavior rather than asocial behavior.
Previous studies have shown that unemployment was the most common cause of hikikomori for residents aged 40–64 years [26]. The current results suggest that a preventive approach to long-term hikikomori could involve mental health and reemployment support for the unemployed population. On the other hand, the active job opening rate, which is the number of jobs available divided by the number of jobseekers, an important indicator of overall employment conditions, did not have a high correlation with hikikomori. As individuals with hikikomori often stop seeking jobs [26], the active job opening rate may not be related to the number of hikikomori cases. Considering that hikikomori cases may not necessarily occur in all countries with a high unemployment rate, sociocultural factors such as family relationships and psychological factors such as personality traits may serve as moderators of the expression of this effect.
Average household income was also not linked to the expression of hikikomori based on the meta-analysis results. This stands to reason, as it is difficult to maintain hikikomori without the support of a household income. However, the results showed that the correlation coefficient of household income varied widely from year to year, indicating no clear correlation between household income and the expression of hikikomori. In addition, considering that Yong and Nomura [19] reported that social class was not significantly different between hikikomori and non-hikikomori cases, further research is needed to clarify the relationship between the family economic situation and expression of hikikomori. The data representing average household income exhibited heterogeneity, and the partial correlation coefficient was different for the data collected from 2010 to 2012 and from 2015 to 2019. Therefore, the relationship between the expression of hikikomori and household income may have changed between 2012 and 2015. This result suggests that various individuals with hikikomori and their families may have started to use support centers and family associations, as the relevant support systems in Japan were enhanced between 2009 and 2013 [41].
There are several limitations to this study. First, while the results showed the relationship between socioeconomic factors and expression of hikikomori, we could not determine causation. Future research is also needed to determine whether other variables, such as mediators and moderators, further affect this relationship.
Second, sample bias is an important limitation. As most of the participants were concerned with solving the problems of their hikikomori family members, the possibility of sample bias cannot be excluded. It is important to note, however, that since individuals with hikikomori are likely to avoid interpersonal situations including treatment [42], research targeting family members may be more expedient and may potentially reduce the effect of the bias of the person with hikikomori. Telephone-based surveys [15] and online counseling via e-mail [43] may also be useful in reducing bias, due to the hikikomori characteristic of avoiding going out, although it may be difficult to reduce the bias due to avoidance of other people. Clinically, family training aimed at easing access to individuals with hikikomori has shown its efficacy [44–46], and may be helpful for engaging the individual with hikikomori in treatment.
Issues with research design robustness are also a limitation of this study. Although long-term follow-up is desirable, dropouts are likely to occur in large-scale follow-up studies, especially given the reclusiveness of hikikomori, or in cases when hikikomori is resolved. This may help explain the dearth of longitudinal studies of hikikomori, though one 12-month follow-up study has been reported in recent years [42]. One way to solve this problem is through Internet-based research; however, considering that the proportion of individuals with hikikomori (29.8%) who use the Internet on a daily basis is lower than that of non-hikikomori individuals (43.3%) [26], this may introduce another source of bias. Moreover, it must be considered whether the findings of this study are applicable outside of Japan, especially in less economically developed countries.
Naturally, in addition to socioeconomic factors, various other biological, psychological, and social factors will influence the expression of hikikomori. Further comprehensive studies are needed to clarify the influence of these additional factors.