all videos were viewed and included in subsequent analyses if tcg was discussed or shown .
most of the search terms used in the current study were obtained from the orlando sentinel and additional terms commonly used in tcg research , including the following : the choking game ; space cowboy ; space monkey ; funky chicken ; pass - out game ; american dream ; blackout ; tingling ; breath play ; choke - out ; dream game ; fainting game ; suffocation ; roulette ; flatliner ; california high ; airplaning ; gasp ; faint challenge ; faint game ; knockout challenge ; choking game instructions ; pass - out ; pass - out challenge ; and knockout game .
each term was searched on march 13 , 2015 , using the standard search parameters for youtube . up to the first 100 videos for each term
were recorded ( 2058 in total ) and then analyzed between march 26 and april 8 , 2015 . at the time of this analysis , some video links were no longer valid , leaving 1857 videos .
the remaining videos were then sorted into those relevant to tcg ( 419 ) and irrelevant to the choking game ( 1438 ) .
a data collection form was used to record information about each video , such as number of views , upload date , whether the video was related to tcg , number of  thumbs up 
ratings , number of  thumbs down  ratings , and the number of comments .
additionally , a number of qualitative aspects of tcg videos were coded to 100% agreement by 3 research assistants .
videos were coded as for prevention purposes if there was any mention of reasons for not engaging in tcg or if they encouraged people to resist participating in tcg .
gender was coded when unambiguous ; if there was any uncertainty , gender was coded as 
 other gender codes for participants , spectators , or assistants included female , male , or mixed when multiple people of either gender were present .
seizures were endorsed if the choking game participant began to visibly convulse , shake , or twitch after passing out .
the presence of other injury was coded if the participant hit their head on losing consciousness .
the number of observers were coded based on who could be seen on the video or if it was clear there was a person holding the camera ( eg , the image was mobile or someone was talking who was out of sight ) .
additionally , videos were coded based on whether someone was actually participating in tcg and , if so , what techniques were shown in the video ( sudden standing , use of a ligature , pressure on the neck , pressure on the chest , use of the  sleeper hold ,  hyperventilation , and breath - holding ) .
coding of asphyxiation techniques was based on the techniques identified by a recent qualitative review of self - asphyxial behaviors . on occasion ,
multiple techniques were used in the video and in these cases all techniques observed were coded .
a one - way anova was used to compare the number of views , ratings , and comments between tcg - related and other videos .
chi - square tests were used to identify significant differences in the frequency of individual techniques , gender of participants , spectators , and assistants , as well as the occurrence of physical injuries .
furthermore , gender differences based on tcg context and techniques used for asphyxiation were analyzed in a final set of  analyses .
an a priori power analysis for a sample size of 500 videos , a moderate effect size ( f = .30 ) , and  = .05 identified the power as 0.98 , which was adequate for the current analyses .
all videos were viewed and included in subsequent analyses if tcg was discussed or shown .
most of the search terms used in the current study were obtained from the orlando sentinel and additional terms commonly used in tcg research , including the following : the choking game ; space cowboy ; space monkey ; funky chicken ; pass - out game ; american dream ; blackout ; tingling ; breath play ; choke - out ; dream game ; fainting game ; suffocation ; roulette ; flatliner ; california high ; airplaning ; gasp ; faint challenge ; faint game ; knockout challenge ; choking game instructions ; pass - out ; pass - out challenge ; and knockout game .
each term was searched on march 13 , 2015 , using the standard search parameters for youtube . up to the first 100 videos for each term
were recorded ( 2058 in total ) and then analyzed between march 26 and april 8 , 2015 . at the time of this analysis , some video links were no longer valid , leaving 1857 videos .
the remaining videos were then sorted into those relevant to tcg ( 419 ) and irrelevant to the choking game ( 1438 ) .
a data collection form was used to record information about each video , such as number of views , upload date , whether the video was related to tcg , number of  thumbs up  ratings , number of  thumbs down  ratings , and the number of comments . additionally , a number of qualitative aspects of tcg videos were coded to 100% agreement by 3 research assistants .
videos were coded as for prevention purposes if there was any mention of reasons for not engaging in tcg or if they encouraged people to resist participating in tcg .
gender was coded when unambiguous ; if there was any uncertainty , gender was coded as 
unclear .  other gender codes for participants , spectators , or assistants included female , male , or mixed when multiple people of either gender were present .
seizures were endorsed if the choking game participant began to visibly convulse , shake , or twitch after passing out .
the presence of other injury was coded if the participant hit their head on losing consciousness .
the number of observers were coded based on who could be seen on the video or if it was clear there was a person holding the camera ( eg , the image was mobile or someone was talking who was out of sight ) .
additionally , videos were coded based on whether someone was actually participating in tcg and , if so , what techniques were shown in the video ( sudden standing , use of a ligature , pressure on the neck , pressure on the chest , use of the  sleeper hold ,  hyperventilation , and breath - holding ) .
coding of asphyxiation techniques was based on the techniques identified by a recent qualitative review of self - asphyxial behaviors . on occasion ,
multiple techniques were used in the video and in these cases all techniques observed were coded .
a one - way anova was used to compare the number of views , ratings , and comments between tcg - related and other videos .
chi - square tests were used to identify significant differences in the frequency of individual techniques , gender of participants , spectators , and assistants , as well as the occurrence of physical injuries . furthermore , gender differences based on tcg context and techniques used for asphyxiation were analyzed in a final set of  analyses .
an a priori power analysis for a sample size of 500 videos , a moderate effect size ( f = .30 ) , and  = .05 identified the power as 0.98 , which was adequate for the current analyses .
using the full list of terms identified by the popular press , as well as several additional terms commonly used in academic work , 419 choking game  related videos were identified and characterized .
see table 1 for full anova results comparing tcg videos to non - tcg videos . when compared to videos that did not depict tcg
tcg videos were also less likely to be commented on , f(1 , 1855 ) = 5.138 , p = .024 .
no significant difference was found between tcg and unrelated videos with regard to the mean number of views or 
anovas comparing the chocking game ( tcg ) videos to unrelated videos and prevention - oriented videos . of the videos related to tcg , only 25% appeared to be intended to prevent future participation .
see table 1 for full results of an anova comparing prevention - oriented to nonprevention - oriented videos . notably , prevention videos had a higher mean number of views relative to nonprevention videos , f(1 , 405 ) = 33.99 , p < .001 .
prevention videos did , however , receive more  thumbs down  ratings than nonprevention videos , f(1 , 405 ) = 14.07 , p < .001 .
prevention videos on average also had more comments than nonprevention tcg videos , f(1 , 405 ) = 5.995 , p = .003 .
no significant difference was found between the number of  thumbs up  ratings of nonprevention videos compared to prevention videos ( see table 1 ) .
such results indicate that , while prevention - oriented tcg videos are viewed more often , they are not reviewed as positively as noncautionary tcg videos .
largely , the videos were filmed by groups of adolescents in private locations , depicting tcg as a group recreational activity .
nearly 80% of the videos , including those intended to be cautionary , included footage of adolescents participating in tcg .
the most common asphyxiation techniques shown included moving quickly from a seated or pronate position to standing in combination with hyperventilation and breath holding .
nearly half of the participants shown in the videos whose gender could be clearly identified were male ( 57% ) compared to 34% female . additionally , 62% of those assisting with inducing asphyxiation whose gender could be clearly identified were male .
the gender of spectators was more diverse , with 29% being exclusively male groups , 14% exclusively female , and 12% mixed gender .
of note , males were significantly more likely to use a sleeper hold than females (  = 14.72 , p = .005 ) .
just over half of the videos showed tcg participants in a private location ( ie , a private residence ) .
one fourth of the videos did , however , show tcg occurring in a public location , such as school property or public sidewalks ( table 2 ) .
a minority of videos showed injury to the participants , including possible seizures demonstrated by convulsions .
one third of the videos showed spectators making an attempt to catch the participant as they lost consciousness .
several significant differences between prevention and nonprevention videos emerged on further analysis . specifically , prevention videos were significantly less likely to depict adolescents actually participating in tcg than nonprevention videos (  = 195.61 , p < .001 ) .
namely , prevention videos were less likely to show participants moving quickly from a seated or squatting position to standing (  = 14.42 , p < .001 ) or pressing on their chest (  = 27.80 , p < .001 ) and more likely to show hyperventilation (  = 11.45 , p = .002 ) and breath holding (  = 7.05 , p = .010 ) .
the representation of the gender of participants in prevention videos also did not represent the gender observed in nonprevention videos , with prevention videos showing significantly more females than nonprevention videos (  = 62.02 , p < .001 ) .
prevention videos also showed tcg occurring in a public location far more often than nonprevention videos (  = 22.77 , p < .001 ) .
overall , while prevention videos had a higher mean number of views , they were rated less positively than nonprevention tcg videos and showed tcg occurring in a significantly different social contexts .
overall , 419 videos pertaining to tcg were found from over 1800 videos that were also identified using common tcg - related keywords .
videos about tcg were less likely to be rated positively and less likely to be commented on than non - tcg videos .
these prevention videos had a higher mean number of views , but also received more 
prevention videos also differed from other tcg videos in their portrayal of the social context of tcg as well as the methods of asphyxiation depicted .
only one prior such study characterized the portrayal of tcg on youtube reviewing only a fraction of the amount of videos examined in the present study .
specifically , based on the videos reviewed by linkletter and colleagues , the number of youtube videos available about tcg has increased by 400% in just 5 years . furthermore , choking game  related videos were viewed over 22 million times , which is a stark increase from the 200 000 views reported by linkletter and colleagues . while this increase in availability and rate of viewing may seem alarming ,
it is consistent with the rapid growth of social media . to extend linkletter and colleagues work , this study reviewed videos that both depicted and discussed tcg , and subsequently coded the videos as either prevention - related or not . using this method , a quarter of the videos from this study
these prevention videos were viewed more often than nonprevention videos , potentially suggesting significant public concern about tcg .
prevention videos were also rated more unfavorably than nonprevention videos , as indicated by youtube s  thumbs down  feature .
furthermore , the differences in prevention video methods and participant gender indicates that there is significant room for growth in future prevention efforts .
notably , many of the prevention videos were home videos recorded using cell - phones and were overwhelmingly not professional or factual .
it is currently understood that relatively few parents speak with their children about the risks of tcg , but parents who do speak with their children about tcg often report using third - party resources .
this observation and the rate at which prevention videos were viewed supports previous claims that a reasonable starting point in tcg prevention may be producing higher quality and more accurate prevention videos that can be accessed through social media in addition to removing existing nonprevention videos .
improved prevention interventions can be designed using the descriptive data from this study regarding those persons present , assisting , and participating .
ideally , using these data will help tailor interventions to those adolescents most at risk of participation . based on the videos reviewed in the current study and consistent with a recent review
when there were groups of spectators , these groups were more often all male than mixed - gender or all female , suggesting that prevention efforts should especially target adolescent male social groups .
males were also more likely to induce asphyxiation using a  chokehold ,  which linkletter and colleagues indicated was associated with a higher risk of serious neurological side effects .
furthermore , most videos were filmed in private locations suggesting a possibility that prevention techniques aimed at informing parents or caregivers about tcg , and assisting in methods of increasing adolescent supervision , may be most effective in decreasing choking game participation .
using existing videos as prevention materials may not be adequate , as many of these videos did not show any kind of injury occurring to the participants and thus may minimize the consequences of participation .
the observed rate of injury is likely low given the estimated rates of serious neurological and other physical side effects associated with tcg .
additionally , it is concerning that though most of the videos showed multiple persons present during asphyxiation , few videos showed any attempt at catching the participant as they lost consciousness .
the apparent lack of safety precautions in the videos reviewed may be due to a lack of concern of the risks of tcg or it may be that adolescents found videos of participants falling more amusing and were more likely to post these online . as a descriptive study designed to highlight the availability and content of choking game  related videos ,
this study only searched for videos using 25 known terms associated with tcg ; however , this list may not be inclusive of all possible common terms for tcg . furthermore , viewing only the first 100 entries of each youtube search could have eliminated a significant portion of the total overall choking game  related videos available on the internet .
additionally , limiting the videos viewed to those that appeared related to our keywords in an initial search may not represent the ways that adolescents identify tcg - related videos in natural circumstances .
based on these limitations , the current study likely significantly underestimates the availability and accessibility of tcg content on youtube . despite this limitation
, the nature of the videos coded in this study can provide insight into how people engage in the tcg in a naturalistic setting , such as location , gender of persons involved , and methods of asphyxiation , as well as how much the availability and viewing of this content has changed in the last five years .
given the wealth of information gathered from youtube about how tcg occurs in a naturalistic setting , future research should move toward developing socially valid and empirically sound prevention materials for adolescents and their parents .
it is clear that since the last methodical analysis of tcg youtube videos in 2010 , the availability of tcg - related materials has increased markedly .
while one quarter of tcg videos available are prevention - oriented , these videos do not reflect naturally occurring tcg nor are they particularly well received . given the significant health risks associated with participation in tcg , the drastic increase in choking game  related videos on youtube within the last five years , and the variety of asphyxial methods in use ,
can be used to design socially valid and scientifically based prevention materials targeted toward those adolescents most at risk for participating in the choking game .
 the choking game ( tcg ) is an adolescent activity in which asphyxiation is used to obtain a  high ,  occasionally resulting in seizures or death . 
 a plethora of tcg information is available through youtube , though this content has not been evaluated recently . 
 the current study described tcg as portrayed in youtube videos and compared views and ratings of tcg videos to unrelated videos . 
 the tcg videos demonstrated diverse methods of asphyxiation , with a minority showing injury to the participants . 
 tcg videos were less likely to be commented on or rated positively than non  choking game videos . 
 tcg prevention videos differed significantly from actual tcg videos in the way they depicted the social context of tcg . 
 thus , tcg videos are accessible through youtube , but the prevention materials available on youtube are not accurate or representative . 
 accurate and educational online prevention materials should be created to decrease the occurrence of tcg . 
Methods
Video Inclusion Criteria
Procedure
Coding Scheme
Data Analytic Plan
Results
Discussion