Demi Lovato has been left "devastated" following the death of her friend

She wrote on her Instagram Stories: "Please hold your loved ones tight. Tell them they are special and that you love them. Make sure they know it. RIP to my boo @sirtruss.

"Addiction is NO joke.. heaven gained this beautiful angel last night because of that terrible disease. I'm crushed and will always miss you @sirtruss. (sic)"

Following Thomas' death, Demi - who has previously battled addiction issues herself - called for people to "ask for help" if they or someone they know is "struggling".

She added: "If you or someone you know is struggling please know it's okay to ask for help. (sic)"

Demi suffered a near-fatal overdose in July last year, and spent time in a treatment centre for addiction.

A month later, the 'Sorry Not Sorry' hitmaker broke her silence for the first time since she was admitted, and thanked her fans for their "positive thoughts and prayers".

She wrote: "I have always been transparent about my journey with addiction. What I've learned is that this illness is not something that disappears or fades with time. It is something I must continue to overcome and have not done yet. I want to thank God for keeping me alive and well. To my fans, I am forever grateful for all of your love and support throughout this past week and beyond. Your positive thoughts and prayers have helped me navigate through this difficult time. I now need time to heal and focus on my sobriety and road to recovery. The love you have all shown will never be forgotten and I look forward to the day where I can say I came out on the other side. I will keep fighting. (sic)"