What evidence from the text supports the idea that Romeo is sad or depressed?

LORD MONTAGUE
Many a morning hath he there been seen,
With tears augmenting the fresh morning's dew,
Adding to clouds more clouds with his deep sighs.
But all so soon as the all-cheering sun
Should in the farthest east begin to draw
The shady curtains from Aurora's bed,
Away from light steals home my heavy son
And private in his chamber pens himself,
Shuts up his windows, locks fair daylight out,
And makes himself an artificial night.
Black and portentous must this humor prove,
Unless good counsel may the cause remove.