News bulletins also have to compete with entertainment programs for their audience and for their prime-time TV slot, and seem to do this by emphasizing emotionally relevant material such as crime, war, famine, etc. at the expense of more positive material.
In the knowledge that the proportion of negatively-valenced emotional material in news bulletins was increasing, in 1997 we conducted a study looking at the psychological effects of viewing negative news items (link is external). We constructed three different 14-min news bulletins. One was made entirely of negative news items, one was made of entirely positive news items (e.g. people winning the lottery, recovering from illness, etc.), and one was made up of items that were emotionally neutral. We then showed these bulletins to three different groups of people. As we predicted, those who watched the negative news bulletin all reported being significantly more anxious and sadder after watching this bulletin than those people who watched either the positive or neutral news bulletin.