Sativa usually produces what is called a "head high" and can be uplifting and energizing. This is not necessarily a function of the THC/CBD ratio. Rather, it is the mix of terpenes coupled with the THC/CBD content that gives you the overall "high". From a medicinal standpoint, it is best to start with a more medicinal product that buds, such as capsules, tinctures, or some other measured dose.
The short, easy answer is: usually for mood conditions. The reality is though, that it’s not about indica, sativa or hybrid but rather, THC, CBD or CBN.