Het gaat om correlaties, dus is het met dit onderzoek niet aangetoond dat het ene het gevolg is van het andere. Al is zo'n oorzaak- gevolg relatie natuurlijk wél een reële mogelijkheid.
uit: Witnessing school bullying carries its own psychological risks
... The findings showed that being a witness to bullying was associated with increased mental health problems and substance abuse, above and beyond the effects of being directly involved in bullying. In other words, witnessing bullying was still significantly associated with psychological measures like anxiety and depression, even after the potential influence of being a bullying victim or perpetrator was factored out. Pupils who'd witnessed bullying (but not been a victim or bully) also tended to report drinking more alcohol than victims or those not at all involved in bullying.
The researchers acknowledged that their study was not longitudinal so it only offered a snapshot of the relations between the various bullying roles and mental health measures. And there's also a need to treat pupils' self-report data with caution. Nonetheless, Rivers' team said their study suggests school psychologists should consider the effects of bullying on bystanders, not just on those directly involved.
Possible reasons why witnessing bulling could be psychologically harmful include being reminded of one's own past experiences of being bullied; being made to feel that one is at risk of being bullied; and also feeling guilty for not intervening to help the victim....
De volledige studie kan je hier lezen: Rivers, I., Poteat, V., Noret, N., & Ashurst, N. (2009). Observing bullying at school: The mental health implications of witness status. School Psychology Quarterly, 24 (4), 211-223 DOI: 10.1037/a0018164