If you want to be calm and happy, make sure  JNK proteins are not suppressing newly generated nerve cells in your hippocampus. From the research below, I’d take an educated guess that learning new things in a happy environment would be a potent remedy for some types of anxiety and depression. 

Researchers have made a ground-breaking discovery revealing new molecular information on how the brain regulates depression and anxiety. In so doing, they identified a new molecule that alleviates anxiety and depressive behaviour in rodents. The research, led by Eleanor Coffey, Research Director at Åbo Akademi University in Finland is a collaborative effort between scientists in Finland and the US.

The researchers found that a protein called JNK when active, represses the generation of new neurons in the hippocampus, a part of the brain that controls emotions and learning. By inhibiting JNK solely in newly generated nerve cells in the hippocampus, the researchers were able to alleviate anxiety and depressive behaviour in mice. This previously unknown mechanism brings fresh insight on how the brain works to regulate mood and indicates that inhibitors of JNK, such as the one used here, can provide a new avenue for anti-depressant and anxiolytic drug development.

Depression and anxiety are highly prevalent disorders and represent one of the largest causes of disability worldwide. These results are important as many patients do not respond to current treatments and it has long been recognised that new mechanistic understanding of these disorders would be necessary to in order to identify drugs for treatment resistant depression.

Researchers used virus tools to find out where in the brain the JNK inhibitor acted to improve mood. They found out the molecule acts to alleviate anxiety and depression by controlling newly born nerve cells in the hippocampus. 

Link

The JNK inhibitor probably has some useful protective function, like not letting new neurons be born into a polluted environment. Some believe toxins or pathogens are the root cause of anxiety and depression. In other words, may be we just need to clean up our planet.