Community is essential to coping with mental health issues of any kind. The most important thing you can do is be supportive. It can be challenging to help a loved one who is self-harming because they are likely to try to hide their behavior.
Self-harm can be correlated with suicidal ideation, but it isn’t always. This is important to remember when reacting to a loved one’s self-harming. Self-harm is generally a coping mechanism for working through pain, isolation, and other negative feelings. Traditional responses to suicidal ideation can often be traumatic, and may worsen these symptoms.
Speaking to a therapist can be helpful for working through the issues that may lead to self-harm, and learning less harmful tools for coping. If a loved one is self-harming, encourage them to connect with someone who has experience treating clients who self-harm.