I believe it's about drug addiction. WARNING - This may contain explicit information about drug use, please don't read if it offends you

Once you've been a heroin addict, there is no true going back. You can change your life, you can end your addiction. But the desire to use, the things you've experienced, they will never truly go away. Places remind you of fond memories of using, they trigger you. People trigger you. Photographs, anything that reminds you, it brings back memories and a desire to use.

"I heard your voice through a photograph" - Referring to seeing a photo that reminded him of drugs even if it isn't even particularly related. Maybe the photo was of a person or a place that reminded him of drugs.

"I thought it up and brought up the past" - It reminded him of his past. Maybe he just thought of heroin or the photo reminded him.

"Stranger things could never change my mind I’ve got to take it on the otherside" - Once you've been to the "other side", ie, you've tried heroin a few times or you've been addicted, there's no going back. You're on the otherside and you're going to have to live there forever. Once you have that desire to use after being triggered it's extremely hard to throw off.

"The ashtray’s full and I’m spillin’ my guts" - Heroin users smoke a lot because it enhances the high. Spillin my guts could refer to vomiting which happens during withdrawal.

"She wants to know am I still a slut" - People often refer to heroin as "she" because the drug can be like an abusive relationship. You love it, it shows you a wonderful time then give you hell. By slut, he is referring to abusing "her" and allowing her to abuse him... Enjoying her like a slut enjoys sex then feeling dirty afterward.

"I Don't believe it's bad" Can be that heroin addicts don't believe it's bad, they know its bad, but well... its hard to explain unless you've been there.

"I yell and tell it that It’s not a friend I tear it down I tear it down And then it’s born again" - You hate the drug, you know it's wrecked your life. It's not your friend, you defeat it, but it so easily comes back. Someone calls you. You're reminded of it by some little reason... You drive past a place you've used... You see a user and you're tempted to "Befriend" them and get contacts.. the list goes on... So many things out there can give you the urge to bring it back into your life.

EXPLICIT CONTENT ABOUT DRUG USE WARNING

"Scarlet starlet and she’s in my bed A candidate for a soul mate bled Push the trigger and pull the thread I’ve got to take it on the otherside" - When you inject, if you use a tourniquet, you tie something around your arm to make the vein show. Then you put the needle in and pull the plunger out to register blood. Before you push it in you "pull the thread" (untie the tourniquet) then push in. Then once you've used once after being clean for a while you're back on that "other side", craving, fighting the drug, all over again. SORRY for being so descriptive and explicit but this is what I understand the lyrics to be in relation to.

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Also the tune of the song is very... reminiscent of the sad and hopeless feeling that haunts your life once you're on that "other side"