One approach to estimate an "average" regression would be to do the following:
- aggregate the data sets
- create a dataset variable (coded 0 for data from the first dataset and 1 for data from the other data set)
- run a multiple regression with the partial slopes you have here (PA & stress) and also run the model with the interaction of these two independent variables with the dataset variable
To proceed, you will need the p-values for the two interaction terms to be zero. If this happens, then you can run the model without the interaction terms, and you can report the "average" partial slopes from the model using the aggregated data set.