Saturn for Karma. It gives benefit according to Karma which was done by you in previous Janma.
Rahu gives covetousness, scheming, unfaithful, dishonest, jealous, foreign culture, against of own traditional, foreign religion, engaging in speculation & smuggling, doing illegal activities.
So if you have Moon Saturn Rahu in one house Rahu will takes the control of particular house & your mindset. So you will have things which i mentioned above. These things will change your mindset. That’s why you are getting mental depression.