BBC News 8 September 2014
Being bullied regularly by a sibling could put children at risk of depression when they are older, a study led by the University of Oxford suggests.
Around 7,000 children aged 12 were asked if they had experienced a sibling saying hurtful things, hitting, ignoring or lying about them.
The children were followed up at 18 and asked about their mental health.
A charity said parents should deal with sibling rivalry before it escalates.
Previous research has suggested that victims of peer bullying can be more susceptible to depression, anxiety and self-harm.
This study claims to be the first to examine bullying by brothers or sisters during childhood for the same psychiatric problems in early adulthood.
Researchers from the Universities of Oxford, Warwick and Bristol and University College London sent questionnaires to thousands of families with 12-year-old children in 2003-04 and went back to them six years later to assess their mental health.