Despite increasing concern over the potential adverse effects of excessive internet use, especially in young people, there is some debate over its definition, magnitude and discriminant validity.

To examine the prevalence of adolescents' internet addiction in Hong Kong, China; to test its differentiation from other correlates; and to examine its relationships with correlates in a representative community sample of adolescents.

A two-wave panel household survey with 208 adolescents (aged 15–19 years) was conducted. Participants were asked to self-report their patterns of internet usage, symptoms of internet addiction, suicidal ideation, psychiatric symptoms and psychosocial conditions during the study period.

The prevalence rate for having five or more symptoms of internet addiction was estimated to be 6.7% (95% CI 3.3–10.2). The discriminatory characteristic of internet addiction was marginally demonstrated. Positive dose–response relationships were found between the number of symptoms of internet addiction and 1-year changes in scores for suicidal ideation and depressive symptoms.

Evidence supports the specificity of internet addiction and its symptoms seem to co-occur with individuals' suicidal ideation and depressive symptoms.

Many people suffer from subthreshold and mild panic disorder and are at risk of developing more severe panic disorder.

This study (trial registration: ISRCTN33407455) was conducted to evaluate the effectiveness of an early group intervention based on cognitive–behavioural principles to reduce panic disorder symptomatology.

Participants with subthreshold or mild panic disorder were recruited from the general population and randomised to the intervention (n = 109) or a waiting-list control group (n = 108). The course was offered by 17 community mental health centres.

In the early intervention group, 43/109 (39%) participants presented with a clinically significant change on the Panic Disorder Severity Scale–Self Report (PDSS–SR) v. 17/108 (16%) in the control group (odds ratio (OR) for favourable treatment response 3.49, 95% CI 1.77–6.88, P = 0.001). The course also had a positive effect on DSM–IV panic disorder status (OR = 1.96, 95% CI=1.05–3.66, P = 0.037). The PDSS–SR symptom reduction was also substantial (between-group standardised mean difference of 0.68). The effects were maintained at 6-month follow-up.

People presenting with subthreshold and mild panic disorder benefit from this brief intervention.