An article by the outlet verywellmind claims that dark chocolate can lower stress levels, but is this actually true? Cortisol is a hormone inside the body that is the main reason behind the feeling of stress, and when the body releases it is when you feel stress. The article's main claim is that eating dark chocolate can acutally lower the cortisol levels inside your body and therefore reduce stress. The author's first piece of evidence is a experiment published in the Journal of the American College of Cardiology, where they took 65 men and women and gave half of them 50 grams of real dark chocolate and the other half  50 grams of "fake" dark chocolate, which was just white chocolate dressed and modified to resemble dark chocolate every day for two weeks. When they observed their stress levels, there was a clear difference in those in the actual experiment and those in the control group, namely, the people who ate the real dark chocolate had a noticable decrease in their cortisol levels. The scientists figured out the main culprit of this difference, it was the flavonoids in the dark chocolate that were absent in the white chocolate. The author then goes on to claim that milk chcolate also offers some help in relieving stress too and cites an experiment published by the International Journal of Health Sciences. This study is similar to the other, only all three types of chocolate were tested (dark, milk, and white). 60 people were seperated into three groups, (10 men and 10 women in each), each with a different type of chocolate. They were given 40 grams of chocolate for two weeks and eveyday completed a percieved stress scale questionaire. Overall, there was a noticable decrease in stress in the groups who ate dark and milk chocolate versus the white chocolate. Overall, the article was not wrong in their claim and provided evidence in their reasoning, it just seems as though the title doesn't specify how much stress is reduced from eating chocolate so it seems just slightly exaggeratory. 
Article from verywellmind: https://www.verywellmind.com/dark-chocolate-health-and-stress-relief-3144564
Study from the Journal of the American College of Cardiology: https://www.jacc.org/doi/10.1016/j.jacc.2014.02.580
Study from the International Journal of Health Sciences: https://pubmed.ncbi.nlm.nih.gov/25780358/