The intervention was CBT-based and consisted of the following six weekly core sessions: Goal setting and motivational interviewing (session 1), impulse control (session 2), problem solving (session 3), cognitive restructuring (session 4), self-worth (session 5), and relapse prevention (session 6). Four weeks after completion of the core sessions, a booster session was provided. The aim of the booster session was to support the user in reflecting and refreshing intervention content and strategies. The user could additionally choose between the following elective sessions: personal needs and values, sleep, relaxation, alcohol and affect regulation, appreciation and gratefulness, and procrastination (see Table 1). The core sessions took approximately 45–60 min to be completed. The user could continue with the following sessions once the previous session was completed. The intervention was guided self-help provided completely online on an internet-based platform of an eHealth provider. The intervention could be completed on any internet-ready device, i.e., PCs, laptops, smartphones, and tablets. The intervention included interactive elements (exercises, quizzes, testimonials, homework) and the user was able to answer questions via text boxes. The answers were then stored within the program and could be viewed by the eCoach and exported in a data format for qualitative evaluation. In addition to the core intervention content in the treatment sessions, the user could use Tiny Tasks, i.e., small exercises and motivational messages via smartphone three times a day. The aim of the tiny tasks was to help the user to transfer the intervention content into their daily lives. They consisted, e.g., of suggestions on how to implement the intervention strategies: “What has influenced your internet usage today?” or “Which features play a key role in contributing to the amount of time you spend online? Are you able to influence those features?”

After completion of each session, the user received content-focused guidance by an eCoach who provided individually manualized feedback (35). The qualification of the eCoaches was at least a bachelor’s degree in psychology. The supervised eCoaches used a treatment manual with standardized text blocks which were individually adapted based on the input and overall progress of each user. Further, there was an internal messaging function on the intervention platform through which the user could contact the eCoach. For a detailed description of the IMI see the study protocol (36).

A case study was conducted as part of a larger RCT to evaluate the efficacy of the intervention. The case study was conducted to analyze and illustrate an individual course of treatment within the framework of the internet-based program. The case report follows the Case Reporting (CARE) guidelines (37). Exemplary symptom reduction and satisfaction of a female student with successful treatment outcome was described. Selection of treatment case considered representativeness of participant characteristics. Case selection followed criteria such as complete treatment course and the transferability of the case through the affiliation to a risk group as a student, as well as through the predominant use of social networks, which has shown to be a represented subtype of IUD among females (9, 11). As a student of young age, she is part of a target group that has been identified as a risk population for IUD (38).

After registering with a self-chosen email address on the study website, the participant received detailed information about the study procedure and was further informed about the possibility to withdraw from the intervention and/or study at any time without any negative consequences. The participant was asked to sign the informed consent together with a data security and confidentiality form. The participant gave informed consent for the participation in the RCT in general and the analysis of her single case in specific. To ensure pseudonymization, we used an individual participant ID number. On the intervention platform, the participant also registered also registered with a self-chosen anonymous email address. Treatment fidelity was assured as all participants received the same intervention on the online platform ensuring that the intervention has been consistently administered. Randomization and allocation of study participants was performed by an independent employee who was not otherwise involved in the study. All study participants were randomized in 1:1 ratio to the intervention or waitlist-control group. A research assistant not otherwise involved in the study performed block randomization with varying block sizes using an automated computer-based random integer generator (Randlist; Datinf GmbH, Tübingen, Germany). All procedures were consistent with the generally accepted standards of ethical practice approved by the Friedrich-Alexander Universität of Erlangen-Nürnberg ethics committee (54_18 B). The trial is registered in the German Clinical Trials Register (DRKS00015314).

To assess feasibility of the IMI, the participant’s course of treatment and the number of completed sessions are reported. We qualitatively evaluated the participant’s written content in each session and analyzed quantitative data from the online pre- (T1) and post-treatment assessments (T2) 7 weeks after randomization. Self-reported data was collected using a secure online-based assessment system (UNIPARK, 256-bit encrypted, EFS Survey, 2016).

The Internet Addiction Test [IAT; (39)] and the Compulsive Internet Use Scale [CIUS; (40)] were used to assess IUD symptoms (see Table 2). Other secondary outcomes included depression [PHQ-9; (41)], insomnia severity [ISI; (42)], anxiety [GAD-7; (43)], procrastination [GSP-K; (44)], alcohol abuse [AUDIT-C; (45)], worries [PSWQ-3; (46)], work-related impairment [WLQ; (47)], health related quality of life [AQoL-8D; (48)], and psychological wellbeing [WHO-5; (49)] (for a complete overview, see Table 3). Efficacy is indicated by reporting change scores. To analyze treatment satisfaction, the Client Satisfaction Questionnaire for internet interventions [CSQ; (50)] was used as well as qualitative analysis of the written feedback given by the participant after each session. The written content of the participant was assessed by open format answers to specific question on the intervention platform. The feedback was recorded on the platform and analyzed by an inductive approach. The feedback asked about (1) perceived usefulness of the session, (2) completion time, (3) treatment elements that the user liked, (4) exercises that were perceived as helpful, (5) components that were not perceived as helpful, (6) perceived support from the testimonials, and (7) suggestions for improvement.

Emma (pseudonym) is a 21-year-old female university student living with her parents and working part-time as a production assistance. She reported to be in a relationship and to have no financial issues. Emma is a first-time treatment seeker with no prior experience with internet-based health programs. She signed up for the intervention because of a constant impairing urge to stay “up to date” on the internet, i.e., refreshing the feeds of her preferred websites. This urge to be on the internet has caused severe difficulties for her to master her daily social and professional tasks. She indicated that at work she spent up to 5–6 h a day on the Internet. The online behavior in her leisure time is primarily characterized by the extensive use of social networks (e.g., Instagram, WhatsApp) and shopping portals in addition to setting up appointments and exchanging email messages. Emma emphasized using the internet as a distraction in stressful situations, which above all leads to problems in her relationship. She also reported efficiency problems and reduced mental well-being due to her excessive internet use. She became aware of the training on the homepage of her university and wanted to participate because the training met her need to cope with her problems on her own.

Emma met the criteria for IUD with a total score of 65 (cut-off ≥49) on the IAT (39) showing high pathological internet use with pronounced symptoms and a score of 49 (cut-off ≥28) on the CIUS (51), indicating problematic compulsive internet use behavior. Her online behavior was characterized by the extensive use of social networks and shopping portals in addition to exchanging email messages corresponding to the subtypes “social networks” and “obsessive research and surfing.” Comorbid symptoms of the participant comprised moderately severe symptoms of depression [17 on PHQ-9; (41)], a moderate level of anxiety [14 on GAD-7; (43)], a tendency to procrastination [31 on GPS-K; (44)], and moderate sleep problems [16 on ISI; (42)]. There were no symptoms of an alcohol use disorder [3 on AUDIT-C; (45)].

Emma aimed at reduced, conscious, and deliberate smartphone use as her training goal. In session 1, she came to the conclusion that her high internet usage is maintained by the advantages that the internet dispels boredom, is fun, gives her a sense of belonging, and distracts her from problems. Her motivation for treatment resulted from relationship issues, the impairment with sleep and efficiency, as well as back pain and headaches (see Table 4).

Emma explained that she has realized through psychoeducation that her use of social networks significantly influences her self-esteem (session 3). She stated that she suffers from the perceived pressure to be perfect through social media. She indicated that online advertising gives her an embellished image of women that makes her feel inferior. She tries to alleviate these feelings of insufficiency by uploading edited images of herself on Instagram in order to receive positive feedback by her followers. To strengthen her self-esteem in real life (session 5), she planned mood-promoting self-care activities (e. g. taking a walk) and formulated affirmative statements about herself and her abilities (e.g., “I am open-minded and honest.”; “I am good at cooking and baking.”) during her IMI participation.

As a strategy to overcome strong urges to update her Instagram feed in the morning, she decided on one of the presented strategies in Session 2 and chose to distract herself by reading the newspaper. Planning positive activities with a weekly schedule to specify time and activity, such as doing yoga, reading a book, taking a bath, and scheduling targeted rewards (e.g., listening to music) served as alternatives to her internet use and strengthened her self-control.

In session 4 on cognitive restructuring, Emma identified the underlying vicious circle of her overall tendency to use the internet as an emotion regulation strategy and described these situations in which she tries to influence her feelings through the internet as “escape moments.” To regulate her feelings independently of the internet, Emma found the thought record for cognitive restructuring particularly helpful (see Table 5). She reported that the thought record enabled her in unpleasant situations (e.g., her boyfriend gazes after another woman), to identify negative thoughts (“She has prettier eyes than me”) and associated emotions such as feelings of worthlessness and self-doubt. By following the instructions of the thought record, she was able to develop positive and helpful thoughts (“My boyfriend loves me. If I start thinking positively, he will do so as well.”), which led to more pleasant feelings and a sense of stability and love in her partnership.

In the following sessions, she repeatedly stated her satisfaction with the “new thoughts.” Following the “writing a letter to yourself”-exercise, Emma realized, that instead of attempting to distract herself with Instagram and followers complimenting her, she tried to become aware of negative thoughts and to take an appreciative attitude towards herself and her relationship (session 6): “Appreciation is very important and I’m getting it back bit by bit.”

To improve her efficiency problems, she chose the elective session on procrastination and tried out different strategies promoting effective time management. She also informed herself about sleep hygiene in another elective session and received strategies on healthy sleep, e. g. not exposing herself to screen light before going to bed. In the sessions “Appreciation & gratefulness” and “Personal needs & values,” she identified important values for herself (“I would like to be there for my family more often.”).

Regarding feasibility, Emma completed all seven core sessions, four elective sessions and four diary entries. On average, she required 0.5–1 h to complete one session and an average of 3 days to go through one core session (range 2–7 days). The participant opted to receive smartphone notifications to accompany the first two sessions.

With regard to symptom reduction, her self-reported symptoms of IUD had decreased from 65 to 44 at post-treatment (7 weeks after randomization) on the IAT corresponding to an improvement to a non-pathological level (cut-off ≥49). There was a decrease from 49 to 32 on the CIUS, showing a reduced symptom severity which was however still above the threshold (cut-off ≥28) for indicating a compulsive internet use (see Table 2). Reduced loss of control (T1: 12, T2: 8) and excessive usage (T1: 13, T2: 9) together with a decrease in perceived salience of internet-related stimuli (T1: 10, T2: 8) were observed. The participant also reported less conflicts in her social (T1: 7, T2: 4) and work environment (T1: 10, T2: 5). Within the qualitative written statements, Emma described a reduction of internet-related thoughts and reported to spend on average 4 h daily online, 3 h less than at the beginning of the training. The self-estimated desire to use the internet had decreased between the first and last week of training from 60–70 to 0%. With regard to comorbidities, the evaluation resulted in a slight reduction of depressive symptoms (T1: 17, T2: 14), anxiety (T1: 14, T2: 12), and procrastination behavior (T1: 31, T2: 23). There was a slight decrease in insomnia (T1: 16, T2: 19) symptoms (for an overview, see Table 3). Each of the main sessions was rated as helpful and the support by testimonials in the sessions was used continuously.

Emma rated the quality of the training as good (CSQ: total score = 21; range 8–32). She stated that she received the kind of treatment she wanted, and the intervention met most of her needs. She was largely satisfied with the level of provided support and the treatment helped her to deal more appropriately with her problems. She would consider the uptake of other online interventions if she needed help in the future and would recommend the intervention to a friend in need.