On the one hand, because they believe in game systems, luck and other thoughts in favor of the player, which makes them keep on trying to win. This is called "magical thinking". They stick to false beliefs: The conviction that success depends on something. The person is convinced that the chance of winning is bigger than normal, based on arguments that cannot be proven, such as:

• The belief in game systems to win.
• The belief in feeling when one is lucky (no good crying over spilt milk).
• The belief that luck is on the right side (the last player has lost everything, so the machine must pay out now).
• The belief in balance (after five times red, it is now black's turn).
• The intensely experienced effect of luck and bad luck.
• The belief that losses can be won back.

On the other hand, gambling becomes more and more a way (that doesn't work) to deal with problems. Gambling can also cause these problems.

Certain drugs can cause gambling addiction, for example this can be a side effect of certain medicines against "restless legs" and "Parkinson's disease" and of alcohol and certain narcotics, for example amphetamines.