The trial began in 2011. A year after starting the drugs, the young people were apparently more likely to report thoughts of wanting to harm themselves. The worry is that perhaps the treatment they received was causing them to have these thoughts of self-harm and suicide.
One of the criticisms of the study, put forward on Newsnight, is the design. The study involved giving the drugs to a group of adolescents and monitoring the effects. However, there was no control group, that is, adolescents who did not receive the drugs. This makes it hard to be sure whether the rates of self-harming thoughts are related to the drugs, would have happened anyway, or perhaps were lower than they would have been without treatment.
It is an important issue because there are high rates of self-harm and thoughts of suicide among children and teens with gender dysphoria.
In other words, they’re nuts.