Excess cannot be summed up in hours spent in front of screens, but rather must be defined in terms of its impact on each individual's life. Many psychiatrists have tried to establish criteria for diagnosing of pathological use of screens. In fact, addiction is partly linked to digital activity, and Internet use is the main cause of addiction. Dr. Young, a psychologist and expert in Internet addiction disorders and online behavior, has therefore proposed an evaluation questionnaire based on eight criteria, linked to Internet use, as a diagnostic aid:
1. Preoccupied with the Internet.
2. Need to use the Internet longer and longer in order to be satisfied.
3. Repeated but unsuccessful efforts to control, reduce or stop Internet use.
4. Agitation or irritability during attempts to reduce or stop Internet use.
5. Stays online longer than expected.
6. Endangerment of, or risk of losing, an important affective relationship, a job, or educational or career opportunities because of the Internet.
7. Lies to family, therapist or others to conceal true extent of Internet use.
8. uses the Internet to escape difficulties or to relieve a dysphoric mood (e.g. feelings of powerlessness, guilt, anxiety, depression).

For further information, we recommend that you consult :

- Institut national du Sommeil et de la Vigilance website
- The Morphée network website (health network dedicated to the management of chronic sleep disorders)
- The ANSES website (Agence nationale de sécurité sanitaire de l'alimentation, de l'environnement et du travail)
- The Santé Publique France website, and its documents on sleep