I believe gambling addiction is a silent killer. There are no symptoms; you may see a healthy person, but deep within, they are suffering from depression and physical disabilities. They may look happy outside, but deep inside, they are lonely and helpless.
We know some addiction symptoms such as spending too much time in gambling, has no ability to stop it (even a day), being easily angry after losses, and some other else. These are some symptoms which are quite visible from the addicts. When someone is suffering a depression, it is also a part of the symptoms. So, we actually can investigate the signs of addiction although it should be checked to the doctors or specialist for a clearer result.
What makes it a silent killer they starts unnoticed until it's accumulated over the years, and all the symptoms appear after so many years of concealing it.
For the addicts, they may be unaware of the symptoms. Yes, it can be called a silent killer if we view it from the side of the addicts. That's why we must be careful and be more sensitive with any change of our habits.