The simple explana- tion is that you've received positive or negative attention that has reinforced your using tantrums as a way to get what you want or to avoid doing what you don't want to do. Since you recognize that tantrums are no longer age-appropriate, the next step is to see your doctor, a psychiatrist & a psychologist to rule out contributing medical or mental health issues, then develop a treatment plan.
No. Temper tantrums arise from the lower part of the brain that is really a computer. When its cells have mild to moderate compromise in oxidative metabolism their acttion becomes grossly exaggerated. Since that is where we generate emotional reflexes, this explains your problem. Please go to my blog "oxygen the spark of life" for further explanation. You can google it.