I would like to know how mazikim, sheidim, se'irim and ruchot rah (often translated as demons or evil spirits) are able to effect our lives. That is, broadly, is their effect physical and psychological? I am not looking for particular examples.
Yearot Devash Derash 1
the Sitra Achra (realm of evil) sucks (yonkim) from the Jew who sins, the holy shefa (flow) inside him, and the Jew is a provider to them. Therefore, "around the wicked they keep walking" (Tehilim 12:9). But, after they sucked from him and his soul has dried up and there is no moisture of holiness left in him, for G-d has left him and his deeds are bad and sinful, what do they do?
They put in his heart the desire to repent to G-d and do good. Then when his soul is fattened with the good of G-d according to his service in performing G-d's mitzvot and he is full of good blessings from G-d, and they see "Yeshurun has become fat" (Devarim 32:15) and his soul is full of good, then they will prevent him from going in the mitzvot of G-d, as each time before, and they suck out from him all the shefa of holiness...
and in Etz Chaim's introduction
And certainly the klipot (forces of evil) will come to fight him to make him sin. Therefore do not come to any sin, even shogeg (unintentional) so that they will not have any shaychut (connection) with you.
both sources from this
Apparently, they have a power to make a sinner sin more. Perhaps this is related to "sin brings sin" in Pirkei Avot and the Talmud's saying "No one sins unless a spirit of folly enters him" (Sotah 3a).
Jewish Encyclopedia in the article 'demonology' ( www.jewishencyclopedia.com/articles/5085-demonology) states:
In the main demons were workers of harm. To them were ascribed . . . various diseases, particularly such as affect the brain and the inner parts . . . .
To cure such diseases it was necessary to draw out the evil demons by certain incantations and tailsmanic performances, in which the Essenes excelled. Josephus, who speaks of demons as "spirits of the wicked which enter into men that are alive and kill them," but which can be driven out by a certain root ([On the Jewish War] vii. 6, § 3), witnessed such a performance in the presence of the emperor Vespasian ([Antiquities of the Jews] viii. 2, § 5), and ascribed its origin to King Solomon.