indexes and keys

Greetings - I hope this is a simple question.

Is there any reason to create an index on a column that already has one
created as part of a SERIAL datatype? That is, I used:

CREATE TABLE personal_data (id serial ...);

to create it, so \d shows:

| postgres | personal_data | table |
| postgres | personal_data | table |
| postgres | personal_data_id_key | index |
| postgres | personal_data_id_seq | sequence |

is there any reason to create another index on id:

CREATE INDEX pd_id_idx on personal_data;

or will the automatically created one be sufficient?

Thanks.

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