Feeling hungry fires up your brain’s “acquisition” systems, the study authors say. Think of it as your “I need something” reflex. And even though the thing you need is food, that reflex makes you more likely to spend money on non-food items, the study shows. So grab a snack before you head to the mall or fire up the laptop for some retail time. And beware these other surprising reasons for your overspending: Your room is messy A disorganized environment—your desk at work, say, or your computer room at home—taxes your brainpower and results in a loss of impulse control. That loss of control makes you more likely to buy stuff, shows a study in the Journal of Consumer Research.   MORE: 7 Ways to Declutter Every Room In Your House You’re sadIf you’re feeling blue, you’ll spend up to four times more than you would if you were feeling “neutral,” finds a report in Psychological Science. Your sense of self-worth drops when you’re down. And new purchases may seem more attractive or valuable when your mind is in that melancholy state, the study authors say.    The sun is outhappiness A little sun brightens your mood, which in turn leads you to spend more than you would if—again—you were feeling “neutral” emotions, shows research from Canada. Wait! you say. How can both sadness and be linked to overspending? The Canadian study authors say sunny feelings lead you to worry less about your spending decisions. You’re shopping alone People tend to form an “emotional attachment” to their favorite stores. This attachment leads them to spend more than they would if they were visiting an unfamiliar spot, shows a study in the Journal of Retailing and Consumer Service. But that emotional attachment disappears if you’re shopping with a friend, which results in less spending and fewer impulse purchases. MORE: Feeling Lonely Is As Unhealthy As Smoking 15 Cigarettes A Day You’ve been hanging out on Facebook Interacting with close friends on social media boosts your self-esteem. And that self-esteem uptick hurts your self-control—especially while shopping, shows a study from Columbia University and the University of Pittsburgh. The research shows people who spent time on social media were more likely to make purchases immediately afterward. MORE: 7 Reasons You’re Tired All The Time