Decision-making is a key activity process that influences many aspects of daily living and both mental and physical health. In general, healthy participants reveal rational choice, but patients with neuropsychiatric disorders reveal irrational and risky choice in decision-making. Addiction is one of typical diseases revealed risky decision-making, addicts select risky action and options that confer short-term rewards at the cost of long-term disadvantages. Thus, irrational and risky decision-making is recognized as a core problem in patients with neuropsychiatric disorders, and a better understanding of the mechanisms underlying altered decision-making would provide insights into potential therapeutic approaches for these diseases. However, the neural pathway and substrates underlying these deficits are particularly unknown. Recently, we found that insular cortex is one of key regions for risky decision-making in an animal model of methamphetamine addiction, by using the designer receptor exclusively activated by designer drug (DREADD) technology, and that GABAergic dysfunction in insular cortex is involved in evaluating the subjective value of reward and reward prediction error. These brain dysfunctions would be related to risk taking behavior in addiction. In this review, we introduced the possible neural pathway related to risky decision-making and behavioral changes in choice strategy using adeno associated virus (AAV).