It just gets addicting. I don't know why. I’m 51 and what am I doing sitting here playing a Farmville game?
Reporter: She spends up to $200 a month on her Farmville habit. She can't help it. She's hooked.
Dr. Timothy Fong of UCLA says he sees patients just like her every day.
The average age of our patient is about 40. We've seen housewives, we've seen doctors, we've seen lawyers. The stereotype of the “video game addict” is a teenage kid in his underwear. That's not what's happening out there.
Reporter: The American Psychiatric Association has so far to recognize video game addiction as a diagnosis. But the American Psychological Association lists video game psychologist as a hot career, because the gaming industry is hiring psychologists as consultants to make their games more enticing. Ariella Leher, a trained psychologist, designs games for middle aged women.
Our most popular title is a game called Murder She Wrote.
Reporter: The content: romance and mystery. But the psychology: pure Las Vegas.
I think there's a lot to learn from Las Vegas.
Reporter: For instance, intermittent rewards.
The rewards, the money in the cash drawer, don't come ever single time. We learned this with rats. With food pedal press.
Reporter: Some games even follow a six second rule. Every six seconds a visual sparkle to entice you to keep playing.
Potency, if you will, of these video games is much, much more intense, more rewarding, more engaging than video games were 30 years ago.
Reporter: Which makes them a lot more fun unless -- do you want 60, do you want 100, 500—you get hooked.