Prevalence of problematic smartphone usage and associated mental health outcomes amongst children and young people: a systematic review, meta-analysis and GRADE of the evidence

Despite concerns about the impact of smartphones on the mental health and wellbeing of CYP, we are unsure of the prevalence of PSU amongst this cohort, and causal associations between PSU and poor mental health have yet to be established. We therefore undertook a systematic review and GRADE of the evidence with the primary aim of characterising the prevalence of PSU amongst CYP, with smartphones as the exposure, and PSU as the outcome. We also undertook a meta-analysis with the secondary objectives of: assessing sociodemographic characteristics associated with PSU; quantifying the impact of PSU on: mental health outcomes; sleep; and school performance. Mental health outcomes assessed included any reported measure of depression or anxiety (diagnosis or screening questionnaire), and perceived stress; sleep quality. In addition, school performance was included as a measure of functional impairment in this population.

The systematic review was carried out according to the PRISMA statement and reported with the PRISMA checklist [20]; furthermore an a priori protocol is registered on PROSPERO (#88800). We included randomised controlled trials; cohort; cross-sectional; and case-control studies. Eligibility criteria included studies of mobile device exposure focusing on children and young people (with a mean population age of no greater than 25) [21]. This broader definition of CYP (recently proposed by Sawyer et al.) was specifically chosen, as it is more inclusive of the CYP population who are developmentally vulnerable to problems such as PSU, and also so as to not overlook important data relevant to the paediatric population. Included studies needed to use a scale with a clear threshold to define PSU. Studies that investigated particular uses of smartphones, such as gambling or gaming, were excluded, as these activities have been identified as addictive in and of themselves [22].

Searches were carried out from January 1st 2011 to October 15th 2017, with no language restriction. This time restriction was specifically chosen to capture studies of current and modern smartphone technology [23]. A search strategy based on the MeSH headings ‘cell phone’, ‘behaviour, addictive’, and ‘adolescent’ (See Additional file 1: Table S1), was applied to 8 databases, including Scopus, Web of Science, ScienceDirect, PubMed, Medline, CINAHL, PsychInfo, and EMBASE, on October 17th, 2017. Two independent researchers (SS, BW) screened the results from the search strategy, and the full texts of all studies that meet these criteria were then further assessed for eligibility. Any disagreements were resolved by discussion with a senior researcher (BC). Additional studies were identified by reviewing the reference sections of relevant papers.

Studies were assessed for methodological quality using a modified Newcastle-Ottawa scale separately for each study design, where each study was assessed and deemed as high, unclear, or low risk of bias across three domains (selection, comparability and outcomes) [24] (See Additional file 1: Table S2). The quality of evidence across the included studies was assessed using GRADE methodology [25]. Study characteristics extracted included: year of study; geographical region; instruments used; response rate; reported prevalence of PSU; mental health; and educational attainment. Study authors were contacted in cases of incomplete data.

We defined PSU in accordance with the literature as smart phone use associated with at least some element of dysfunctional use, such as anxiety when the phone was not available, or neglect of other activities [13, 18]. This was measured by included studies using a range of scales, such as the Smartphone Addiction Scale (SAS) or the Mobile Phone Problematic Use Scale (MPPUS) [13, 14]. We summarise each of the instrument definitions used, and highlight the behavioural domains in Additional file 1:Table S4 and S5.

Heterogeneity exceeding 85% was explored using subgroup analyses [23]. Pre-determined subgroup analyses included: study quality assessment; age; gender; high PSU prevalence (> 40%); time period of study; and geographical region.

After protocol registration, the following additional outcomes were included: suicidal ideation, and associated psychological factors.

Of 924 studies identified, 41 studies were included in this review (Fig. 1). Of those, 22 studies were deemed to be of poor methodological quality, and 19 of moderate quality (See Additional file 1: Table S2). Three cohort and 38 cross-sectional studies were included, with 41,871 participants, 55% of which were female. Included studies were conducted in Europe (n = 9), Asia (n = 30), and America (n = 2) (See Additional file 1: Table S3). There was wide variability in the definitions of PSU (See Additional file 1: Table S4), and the criteria used ranged from a single criterion such as psychological withdrawal phenomena (n = 2), to measurement of tolerance, withdrawal, loss of control, preoccupation, neglect of other activities and evidence of harm, which form the criteria for behavioural addictions (n = 19) (See Additional file 1: Table S5).

Communication was the most frequent type of smartphone usage by those with PSU, reported by 14 studies [28‐39]. Problematic users reported that social networking was the most important or preferred activity on smartphones [34, 40]. ‘Addicted’ or ‘problem user’ groups were linked with particular phone uses: TV watching [35] and social networking [37, 38]. Lee and Lee [41] found that use of phones to gain peer acceptance was the most significant type of use related to PSU.

Both substance use and other behavioural addictions were associated with PSU. Internet addiction [33, 42‐44], Facebook addiction [31], compulsive buying [43], increased alcohol use [42], and cigarette smoking [42] were also found to be positively associated with PSU.

Across 14 studies, age was correlated with PSU [28‐33, 40‐42, 45‐49], and 17 to 19 year-olds were the most frequent sufferers of PSU. Females were reported as more prone to PSU by 13 studies [31‐34, 40, 41, 48‐54]; however 4 studies reported the opposite [35, 46, 55, 56]. PSU in males was correlated with use of media applications and games, while in females it was correlated with communication and social networking applications [28]. PSU was also positively associated with monthly cost of living [28], family income [36], and a higher economic status [42].

Prevalence was assessed using 24 different questionnaires, with the most common being the Smartphone Addiction Scale, Short Version (SAS-SV; n = 7) and the Smartphone Addiction Proneness Scale (SAPS; n = 5), for further details (See Additional file 1: Table S4).

The majority of studies (n = 31) found a prevalence between 10 and 30%, and the median was 23.3% (interquartile range 14–31%, Fig. 2).

PSU has been consistently associated with measures of poor mental health, in particular relating to depression, anxiety, stress, poor sleep quality, and day to day functional impairment demonstrated by poor educational attainment. Of the studies included, 20 investigated the relationship between PSU and mental health amongst CYP. This is summarized in a qualitative synthesis (See Additional file 1: Table S6).

PSU shares many traits with substance abuse disorders and behavioural addictions [13‐18], and it appears to be common. This is unsurprising considering that those at risk of PSU have similar traits to those at risk of other addictions. Like alcohol, smartphone use is socially acceptable and widely available. In addition, smartphones are seen to facilitate work and education, as well as leisure. PSU therefore poses a different and arguably much bigger public health problem than substances of abuse or even Internet gaming. The pathogenesis of PSU is poorly understood and likely complex [45, 68, 69]. Some have suggested that the continued interconnectedness and anticipation of response plays a role [23].

The incidence of mental health conditions amongst CYP has increased substantially over the last ten years, representing a significant burden on healthcare systems worldwide [6, 8, 70, 71]. The reason for this increase in incidence is unknown, but has been most notable amongst adolescent females, the same cohort shown to be most at risk of PSU in our review [5]. This has parallels between the 68% increase in self harm rates in the UK since 2011, at the same time as the widespread introduction of smartphones [72]. Studies have previously suggested that PSU may at least partly underlie this epidemiological shift. Given the frequency of PSU amongst CYP and its significant association with symptoms of common mental disorders, as highlighted by our review, this relationship and consideration of PSU as a potential causative factor requires urgent further exploration.

This work is strengthened by the inclusion of studies from wide geographical regions that reported consistent and plausible findings. However, given the nature of the review question, studies were non-randomised and at a high risk of bias. Weaknesses of implementation include varying definitions and thresholds for PSU, some of which were incompletely described. Mental health outcomes were all responses to self-report questionnaires rather than formal diagnoses, suicidal acts or referral to secondary child and adolescent mental health service care, raising the possibility that these are sub-threshold symptoms. Furthermore, reverse causality cannot be excluded as rationale for the associations found.

Our review indicates that approximately 1 in 4 CYP are demonstrating problematic smartphone use, a pattern of behaviour that mirrors that of a behavioural addiction. A consistent relationship has been demonstrated between PSU and deleterious mental health symptoms including: depression; anxiety; high levels of perceived stress; and poor sleep. Younger populations are more vulnerable to psychopathological developments, and harmful behaviours and mental health conditions established in childhood can shape the subsequent life course. Further work is urgently needed to develop assessment tools for PSU, and prevent possible long-term widespread harmful impact on this and future generations’ mental health and wellbeing. In particular, longitudinal studies are required to characterize the causality of the relationships found in this study between PSU and mental health. Possible research could include cohort studies looking at changes in experience of psychopathological symptoms in relation to changes in PSU levels, or a randomized controlled trial comparing the impact of smartphone use, for example in terms of duration or time of day, on mental health outcomes. Future studies should assess the impact of PSU on more objectively evaluated health outcomes, such as depression or anxiety disorders as detected by structured diagnostic instruments (eg the DSM-5 criteria), referrals to secondary mental health services, or primary care psychological therapies services, or prescriptions for medications such as antidepressants.

The prevalence of PSU amongst CYP and its association with symptoms of common mental disorders is a growing public health problem and as such, it should be a concern to policy makers. To address PSU amongst CYP, an accepted and validated diagnostic definition is firstly required, to systematically identify those suffering. Healthcare providers should recognise that excessive or night-time use of smartphones may play a role in the aetiology of mental health and wellbeing problems amongst CYP presenting to their practice. Primary prevention of PSU is difficult given that smartphone use is now a societal norm; however, awareness of the risks of PSU amongst CYP, parents, teachers and healthcare providers could help limit exposure. Further research should develop a consensus regarding the most appropriate diagnostic criteria for PSU, and determine risk factors for PSU. Finally, further exploration of the relationship between PSU and diagnosed mental health conditions is urgently needed to clarify the magnitude of any casual contribution of PSU to the growing burden of mental health conditions amongst CYP.