The control group will receive health talks about internet addiction consequences and impacts on young people by nursing students who are not involved in the intervention group to mimic the time and attention spent on the intervention group. These health talks are considered routine care for IA health promotion.

Calculated by dividing the number of secondary school students who returned questionnaires by the number of questionnaires distributed. This will be calculated by groups at baseline and each follow-up.

Calculated as the percentage of missing values in the dataset. Unknown or blank values will be considered missing values.

Are defined as unfavorable and unintended events that are not present at baseline, or appear to have worsened during the study. The relation to the intervention will be assessed in accordance with the protocol for adverse events management (It can be provided upon request). The number and event severity will be recorded. Numbers and reasons for exclusions will be noted.

Measured by the number of IA symptoms via a self-reported questionnaire.

Measured by the number of IA symptoms via a self-reported questionnaire.

CES-DC will be used to record the number of depression symptoms in secondary schools students with IA at each follow-up. It includes 20 items asking on a 4-point Likert scale in relation to the incidence of the stated symptoms during the previous week, and are scored from 0 to 3 (0 = not at all, 3 = a lot). Total scores range from 0 to 60, with higher scores indicating greater number of depressive symptoms. This questionnaire has been empirically tested and validated in Hong Kong children and are currently using in Youth Quitline.

CES-DC will be used to record the number of depression symptoms in secondary schools students with IA at each follow-up. It includes 20 items asking on a 4-point Likert scale in relation to the incidence of the stated symptoms during the previous week, and are scored from 0 to 3 (0 = not at all, 3 = a lot). Total scores range from 0 to 60, with higher scores indicating greater number of depressive symptoms. This questionnaire has been empirically tested and validated in Hong Kong children and are currently using in Youth Quitline.

CES-DC will be used to record the number of depression symptoms in secondary schools students with IA at each follow-up. It includes 20 items asking on a 4-point Likert scale in relation to the incidence of the stated symptoms during the previous week, and are scored from 0 to 3 (0 = not at all, 3 = a lot). Total scores range from 0 to 60, with higher scores indicating greater number of depressive symptoms. This questionnaire has been empirically tested and validated in Hong Kong children and are currently using in Youth Quitline.

CES-DC will be used to record the number of depression symptoms in secondary schools students with IA at each follow-up. It includes 20 items asking on a 4-point Likert scale in relation to the incidence of the stated symptoms during the previous week, and are scored from 0 to 3 (0 = not at all, 3 = a lot). Total scores range from 0 to 60, with higher scores indicating greater number of depressive symptoms. This questionnaire has been empirically tested and validated in Hong Kong children and are currently using in Youth Quitline.

The anxiety level of secondary school students with IA will be measured by the short form of the Chinese Version of the State Anxiety Scale for Children (CSAS-C) at each follow-up. It has 10 itmes with scores from 1 to 3. Total scores range from 10 to 30, with higher scores indicating a higher level of anxiety. This questionnaire has been empirically tested and validated in Hong Kong children.

The anxiety level of secondary school students with IA will be measured by the short form of the Chinese Version of the State Anxiety Scale for Children (CSAS-C) at each follow-up. It has 10 itmes with scores from 1 to 3. Total scores range from 10 to 30, with higher scores indicating a higher level of anxiety. This questionnaire has been empirically tested and validated in Hong Kong children.

The anxiety level of secondary school students with IA will be measured by the short form of the Chinese Version of the State Anxiety Scale for Children (CSAS-C) at each follow-up. It has 10 itmes with scores from 1 to 3. Total scores range from 10 to 30, with higher scores indicating a higher level of anxiety. This questionnaire has been empirically tested and validated in Hong Kong children.

The anxiety level of secondary school students with IA will be measured by the short form of the Chinese Version of the State Anxiety Scale for Children (CSAS-C) at each follow-up. It has 10 itmes with scores from 1 to 3. Total scores range from 10 to 30, with higher scores indicating a higher level of anxiety. This questionnaire has been empirically tested and validated in Hong Kong children.

It contains 19 items measuring 7 domains: subjective sleep quality, latency, duration, habitual efficiency, disturbances, use of medication, and daytime dysfunction on a 3-point scale (0: no difficulty to 3: severe difficulty) except for the items reporting bedtime and time awake. The sum of the seven component scores produces a global score with higher scores represent poorer subjective sleep quality. It has been validated in Hong Kong children and adolescents previously.

It contains 19 items measuring 7 domains: subjective sleep quality, latency, duration, habitual efficiency, disturbances, use of medication, and daytime dysfunction on a 3-point scale (0: no difficulty to 3: severe difficulty) except for the items reporting bedtime and time awake. The sum of the seven component scores produces a global score with higher scores represent poorer subjective sleep quality. It has been validated in Hong Kong children and adolescents previously.

It contains 19 items measuring 7 domains: subjective sleep quality, latency, duration, habitual efficiency, disturbances, use of medication, and daytime dysfunction on a 3-point scale (0: no difficulty to 3: severe difficulty) except for the items reporting bedtime and time awake. The sum of the seven component scores produces a global score with higher scores represent poorer subjective sleep quality. It has been validated in Hong Kong children and adolescents previously.

It contains 19 items measuring 7 domains: subjective sleep quality, latency, duration, habitual efficiency, disturbances, use of medication, and daytime dysfunction on a 3-point scale (0: no difficulty to 3: severe difficulty) except for the items reporting bedtime and time awake. The sum of the seven component scores produces a global score with higher scores represent poorer subjective sleep quality. It has been validated in Hong Kong children and adolescents previously.