in my story, for plot reasons, my character is in recovery for three weeks from a concussion. there’s no memory loss, but she passes out for 10 seconds and when she wakes up she’s nauseous and has slurred speech + ringing ears. how hard would she have to get hit in the head to have a concussion that is that severe?
This is going to be a bit nitpicky, and it’s not going to give you the answer you’re looking for, so, before we start, sorry about that.
Being knocked unconscious is a Type 3 Concussion (minimum). Nausea, slurred speech, and ringing in the ears are consistent with a concussion. For a Type 3, a recovery time between a week and a month is reasonable.
The rating for types work as follows:
Type 1 Concussions do not result in a loss of consciousness, and symptoms (or, at least, most symptoms) subside within ~15 minutes of the injury.
Type 2 Concussions do not result in a loss of consciousness, and symptoms persist beyond 15 minutes. Recovery usually occurs within 10 days of the injury.
Before we keep going, the symptom list is a bit longer than what you listed above. It can include: Confusion, impaired fine motor control, headache, nausea, vomiting, vertigo, sensitivity to light and/or sound (I think the other senses too, but I’m not 100% certain), difficulty with concentration and thinking, irritability, amnesia. (Also missing a few. This is brain damage we’re talking about, and it can scramble a lot.) (Also note, Type 1 Concussions usually only have mild symptoms, such as headaches and mild nausea. The more severe symptoms will, usually, push it into a Type 2 because they don’t go away.)
Also, before we keep going, worth singling out amnesia for a second. This one gets seriously misrepresented in pop culture. Realistically we’re talking about someone losing some time around the concussion. They may not remember what lead up to the injury, or missing a couple hours after it, and never will. Global, “I can’t remember anything,” amnesia is incredibly rare.
Type 3 Concussions get to pick off the full symptom list above (it won’t have everything, but it’s not limited the way a Type 1 is.) It also comes with less than 60 seconds of unconsciousness. Full recovery usually takes between 10 and 30 days. This is what you’re describing.
Type 4 Concussions involve being unconscious for more than 60 seconds, and recovery time can range from a couple weeks to more than a month.
With all of that said, what you’re asking is, “how hard does she have to be hit in the head?” The answer is, “hard enough.”
Concussions, and most brain injuries, aren’t about how hard you’re hit, it’s about what happens to your brain after you’re struck. A concussion is a bruise on the brain itself. Usually, the head is jostled, and the brain bounces off the interior of the skull, causing injury. This is just like any other bruise except the tissue being damaged is responsible for regulating the rest of your body. A relatively light hit to the head can cause a Type 4 Concussion and kill you. Conversely, you can take some horrific abuse to the head, and not suffer a concussion at all.
If you’ve been digging through medical write ups on websites and trying to figure out how hard someone needs to be hit, the answer is there’s no concrete rule. From a medical standpoint, concussions are about where you ended up, not how you got there.
Finally, recovery times are directly related to how well someone follows medical advice on recovering. There’s a lot of things that are personal to the individual and their concussion. Ex: you may not have trouble watching TV, but others will, and with a future concussion, you might.
Also, further muddying things, multiple concussions are cumulative, even over a long period of time. So, if you’ve suffered a concussion, you’re at greater risk of suffering future concussions from head trauma. Something to keep in mind if your character’s recovering from one.
Concussions are very serious injuries. If you suffer one, even a Type 1, you really should see a doctor, and follow their advice while your brain heals.