Mental Imagery Tasks to Reduce Internet Gaming Disorder (IGD) Cravings

Inclusion Criteria: * The scores of the 9 items of The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition(DSM-5) recommended diagnosis for Internet gaming disorder ≥ 5. * Engagement in popular Internet games (e.g. Arena of Valor, League of Legends and Player Unknown's Battle Grounds) for over 20 hours per week for a minimum of 12 months. * The scores of the Young-Internet Addiction Test(Y-IAT) ≥ 50 Exclusion Criteria: * Current or history of use of illegal substances and gambling; * Current or history of psychiatric or neurological illness; * Current use of psychotropic medications.