Table 1.

Construct Description, Sample Descriptives and Correlations

Construct and Description	Mean(SD) or Percent	Hours of Sleep (r)	Bedtime (r)
Social Media and Internet Use
Frequency of social media: “On a typical school week, how often do you check.... Social Media (like Instagram)”a	3.78 (1.92)	−0.18**	0.25**
Problematic internet behaviors (3 items): “How often do you: Lose motivation to do other things that need to get done because of the internet?”; “Feel nervous or anxious when you’re NOT online?”; “Become moody or depressed when you’re not online?” (Cronbach’s alpha=.74)b	1.85 (.83)	−0.23**	0.19**
Fear of missing out (3 items): “I get worried when I find out my friends are having fun without me.”; “Sometimes, I wonder if I spend too much time keeping up with what is going on.”; “When I have a good time it is important to update my status and share the details online.” (Cronbach’s alpha=.60)c	1.61 (.62)	−0.16**	0.19**
Loss of sleep due to internet use: “How often do you: Lose sleep because you can’t quit what you’re doing online?”b	1.81 (1.04)	−0.40**	0.37**
Problematic digital technology use (3 items): “When my mobile phone alerts me to indicate new messages, I cannot resist checking them.”, “I often think about calls or messages I might receive on my mobile phone.”, “I feel like I use my mobile phone too much.” (Cronbach’s alpha=.68)d	2.61 (1.01)	−0.20**	0.19**
Often watch emotionally disturbing videos: “How often do you watch emotionally disturbing videos on YouTube or the Internet (e.g., scary, tragic)?”b	1.75 (1.05)	−0.22**	0.20**
Often watch violent or disturbing videos: “How often do you watch violent or disturbing videos on YouTube or the Internet (e.g., rated R)?”b	1.73 (1.10)	−0.25**	0.25**
Websites/Social Media Posts
Weight messages: “ways to be very thin (such as being anorexic)”e	15%	−0.17**	0.14**
Hate messages: “hate messages that attack certain groups or individuals”e	20%	−0.10**	0.13**
Drugs/drinking: “sharing experiences of taking drugs or drinking”e	17%	−0.18**	0.24**
Self-harm: “ways of physically harming or hurting themselves”e	13%	−0.15**	0.17**
Behaviors within 1 hour of sleep
Watch YouTube videosf	2.51 (1.24)	−0.30**	0.32**
Text friendsf	2.21 (1.17)	−0.25**	0.33**
Check social mediaf	2.26 (1.26)	−0.28**	0.36**
Play online gamesf	1.77 (1.03)	−0.17**	0.20**
Read a book/kindlef	1.68 (.99)	0.06	−0.16**
Eat a snack or treatf	2.15 (1.10)	−0.17**	0.20**
Phone Use and restrictions
Frequency of text messages: “On a typical school week, how often do you check....Text or Imessages”a	3.94 (1.53)	−0.18**	0.21**
Screen restrictions at bedtime: “When are you NOT allowed to use your phone or go online?... At bedtime”e	50%	0.22**	−0.27**
Age received smartphone: “How old were you when you first got your own smartphone (with internet)?”g	10.40 (1.35)	0.08*	−0.16**

^aResponse scale: 1= Never/Does not apply to 6= More than every hour

^bResponse scale: 1= Never to 5=Very Often

^cResponse scale: 1= Not at all true of me to 4= Extremely true of me

^dResponse scale: 1= Strongly Disagree to 5=Strongly Agree

^eResponse scale: 0=No, 1=Yes

^fResponse scale: 1= Never to 4= Most nights

^gResponse scale: 8= 8 yrs or younger to 14= 14 yrs and older

^*p<.05,

^**p<.01