What do 即 (jí) and 已 (yǐ) do in the sentence 病征在成年早期即已显露 ("symptoms become visible at early adulthood")? In a document about 边缘性人格障碍 (biānyuán xìng réngé zhàng'ài) = "Borderline Personality Disorder", we have the following sentence:


  病征在成年早期即已显露，但随年龄增长趋于缓和或稳定。
  Bìngzhēng zài chéngnián zǎoqí jí yǐ xiǎnlù, dàn suí niánlíng zēngzhǎng qū yú huǎnhé huò wěndìng.  


I translate this to:


  Symptoms become visible at early adulthood, but with age they have an increasing tendency to alleviate or stabilize.


I think it's a reasonably accurate translation.  (Google Translate gives a translation that's much the same: "Symptoms are revealed early in adulthood, but tend to ease or stabilize with age.")

What I'm confused about is the use of


即 (jí), which means something like "namely" (also mentioned in What does 即 mean in this sentence?), but I don't think that makes sense here, and
已 (yǐ), which means something like "already".


Neither of these makes sense to me in this context.

Question: What do 即 and 已 do in the sentence 病征在成年早期即已显露?

There's a few examples of 即已 used together on YouDao, but I don't see how they help.
病征在成年早期即已显露


即 here means 就. It means this sense: 



So, 病征在成年早期即已显露 is equal to say 病征在成年早期就已显露.