Counting number of days sick per condition

Hello.

I’ve got a long spreadsheet with many rows (>5000). Each row relates to a time someone has been off work sick. In two columns (D and G) I have “reasons” for sickness and “Days lost” due to sickens respectively.

I have set up a look-up type formal to search for the reasons for sickness (=COUNTIF($D$4:$D$5955,I4), which obviously simply counts the number of times “stress”, for example, appears in my list.
Is it then possible to create a formula to count the number of days lost due to a certain condition without having to calculate this manually? So, the spreadsheet would look up all “stress” in column D and adds up its related value in column G for each “stress”?

Hope that makes sense?

Many thanks

B