Are Suicidal Thoughts Evidence That Someone Is Demonized?

No.

First, everyday people may occasionally deal with an unreasonable thought to drive their car into something or jump off of something to kill themselves.  That means they’re tempted by an evil spirit, but that doesn’t mean they’re demonized in the sense of needing deliverance.

I remember visiting a certain city and just minding my own business one morning on a high hotel balcony when I had this sudden thought, “Just jump off and end it all.”  I was NOT demonized.  However, once I rejected that thought, the follow-up devilish thought was, “You have a problem.  Normal people don’t have thoughts like that.”  I got into a service where I was serving in a “helps” capacity for an anointed preacher, and the preacher said, “The weirdest thing happened this morning.  I was just out on my balcony and I had the sudden thought to jump off and kill myself.”  Neither one of us was actually demonized, though obviously a certain demon was making the rounds.  You do not need deliverance just because you had a thought like that.

Second, Jesus definitely did NOT have a demon, but the devil tried to get HIM to commit suicide by jumping off a tall building.  The devil brought the thought to Him just as he could to godly believers who don’t need deliverance.

Third, a demonized person MAY be suicidal, as was the boy in Mark 9:17-29, but not ALL suicidal people need to be delivered from “spirits of suicide.”  In fact, that kind of oversimplification can lead to a mentally ill person not getting needed other kinds of help because well-meaning church people just assume that “binding that spirit of suicide” will fix everything.  People can take their lives just because they’re depressed without being explicitly demonized, especially if they disobey Philippians 4:8 and feed on bad news all day, which is easy to do.  News outlets know that bad news attracts a wider audience than good news, so guess which kind of news they deliberately put out all day!  The fact that they put it out all day doesn’t mean that you have to listen to it all day, and you shouldn’t.

Fourth, someone might be having suicidal thoughts because they're a known possible side effect of one of those drugs relentlessly advertised on TV.

Fifth, we always need to turn to Scripture for our answers.  Did people in the Bible commit suicide because a spirit of suicide got to them?

Samson killed himself.  King Saul killed himself.  Ahithophel killed himself.  Zimri killed himself.  Judas Iscariot killed himself.  In NONE of these cases is there a mention that any “spirit of suicide” was involved in the process.  For various reasons, these men wanted to die and they ended their own lives.

So we would be “pushing it” to assume that a “suicide spirit” must be involved with any attempted or “successful” suicide.  And we would be pushing it even farther to claim that suicidal thoughts are evidence that someone is demonized and needs deliverance.  It is possible (as with the boy mentioned above) that a spirit would try to get someone to end his life, but the fact that someone is wrestling with suicidal thoughts does not prove he has a demon.