Technology usage is today's equivalent of meeting in the park after schools for teens and in an age where social media is available at our fingertips, there is going to be, amongst school age peer groups, an element of bullying. Bullying in the park wasn't seen by parents but it still existed!
I don't think it is the cause of poor mental health. The cause is deep within the person themselves and being unable to seek the correct supportive help. Some people just don't want to be here, they need support and the ability to make that decision and look at the alternatives.
Those with genuine suicidal thoughts all have some kind of leakage of those thoughts (talk about suicide, internet history on sites about suicide and letters/ notes about dying). Parents need to act on behavioural changes in their child and not ignore and label it as, 'being a teenager'
With thoughts of self-harm comes low self-esteem, anxiety, irritability and often volatile emotions and mood swings and reckless actions thoughts or conversations. All this can cause exhaustion and excess sleeping, withdrawal from others, secretive internet use and starting to drop back in studies, peer friendships and distancing themselves from people who 'don't understand'. These signs are often recognised and misread.
Many young people do try to seek help before attempting suicide by telling other people about their feelings or by self-harming to show people that they are in emotional pain. Often they seek help in the wrong places and don't get the support they need.
On balance, no I don't blame social media, I blame a broken society with a huge lack of mental health resources for decades, now slowly arriving and a change where it is now OK to talk about mental health rather than a stigma. I blame the fast pace and huge expectations in today's society where success is measured in monetary terms.
Suicide figures are kept quiet because the figure is far higher than expected. Most suicides don't even make the local papers any more unless unusual in some way.