Table 5.

Study participants and descriptive statistics of the study variables by study year, %

	Missing data1		2013 N = 178,706	2015 N = 118,772	2021 N = 156,478
Socio-demographic variables
Gender	0.1/0.0
Female			51.0	51.7	52.8
Male			49.0	48.3	47.2
Age group	0.2/0.0
13–15 years			43.3	33.7	46.4
16–17 years			45.9	52.8	44.9
18–20 years			10.8	13.5	8.6
Higher parental education2	4.8/4.3		46.3	45.7	56.6
Living with both parents	2.9/2.5		65.3	63.7	67.1
Immigrant status/family origin	2.5/2.1
Finnish origin			90.2	89.0	87.0
One parent of foreign origin			5.7	6.2	7.4
Foreign origin, born in Finland			1.5	1.7	2.2
Foreign origin, not born in Finland			2.7	3.1	3.4
Region of Finland3	0.0/0.0
Southern Finland			39.2	39.2	38.8
Southwestern Finland			12.7	14.0	12.4
Eastern Finland			10.7	10.4	9.7
Western and Inland Finland			23.1	22.7	24.0
Northern Finland			10.1	10.3	11.3
Lapland			3.6	2.9	3.2
Åland			0.6	0.6	0.6
Psychiatric symptoms: control variables
Generalized anxiety (GAD-7 ≥ 10)	1.0/0.3		10.9	11.6	19.6
Depressed (PHQ-2 ≥ 3)	2.2/1.44				21.1
Psychiatric symptoms: outcome measure
Social anxiety (Mini-SPIN ≥ 6)	1.9/0.0		19.3	21.5	34.8

¹Of all participants (before slash) / of those fulfilling the inclusion criteria for the study (after slash)

²At least one parent with university degree

³Based on Regional State Administrative Agencies

⁴Considering year 2021 when PHQ-2 was available

Note: Information on age was missing from 6620 (1.4%) survey forms. These responses were coded with mode age of the grade the participant was in. Age reporting was unreliable (e.g., lower than 15 years in upper secondary education) in 850 (0.2%) forms. Responses were coded as missing information and thereby excluded from the analyses. Only 403 respondents aged 13 years in the age group of 13–15-year-olds. For years 2013, 2015, and 2021 in total there were 439 (0.1%) survey forms with missing information on official gender. They were excluded from the analyses