Book excerpt: Anxiety, depression and addiction are the scourge of modern-day living. How are they linked? How do we beat them? According to bestselling author and researcher David Gillespie, we are more addicted than ever before, which is playing havoc with our dopamine levels. This is fuelling epidemic-like levels of depression, anxiety and stress. Gillespie reveals a large and robust body of research that shows how addictive activities, such as screen use, sugar consumption, drinking, gambling, shopping and smoking, spike our dopamine levels. This, in turn, affects our brain's ability to regulate our mood. The good news is that we can break the cycle to make things better. There are myriad root causes of mental illness, many of which are beyond our control; David argues that it makes sense to tackle the thing that is within our control - our see-sawing dopamine levels. Packed with cutting-edge research and practical advice, David's latest book arms us with the tools we need to break our addictions, conquer uncertainty and reset our brains.