It can be scary when you realise you know someone who needs help. Let your friend know you care, and spend time with them. Just knowing that somebody cares about them can be reassuring as they may feel very alone and as if no one cares. If you are usure about what to say to your friend or how to approach the situation, try telling your friend that you are worried about them and try to figure out why your friend may be feeling the way they are.
If they do talk to you about how they’re feeling, it might help if you acknowledge that they are feeling down and things might seem hard, while at the same time trying to remain positive and encouraging.